Hemrfacial Spasm: Evaluation by Magnetic Resonance Imaging and Magnetic Resonance Tomographc Angiography Charles H. Adler, MD, PhD,* Robert A. Zimmerman, MD,I Peter J. Savino, MD$I Bruno Bernardi, MD,$ Thomas M. Bosley, MD," and Robert C. Sergott, MD$"
We evaluated 37 patients with hemifacial spasm and 16 age-matched control patients with other neurological disorders using magnetic resonance (MR) imaging, MR angiography, and MR tomographic angiography. MR tomographic angiography is a new technique using computer reconstruction of MR angiographic images to create coronal angiotomes that display tissue and arterial structures on the same image. Twenty-four of 37 (64.9%)patients with hemifacial spasm had ipsilateral vascular compression of cranial nerve VII or the pons noted by this technique, whereas only I of 16 (6.3%)control patients had compression. MR imaging and MR angiography were less sensitive and less specific in evaluating for vascular compression. This study supports vascular compression of cranial nerve VII or the pons as a cause of hemifacial spasm, and demonstrates MR tomographic angiography's value as an excellent, noninvasive technique to demonstrate the compression. Adler CH, Zimrnerman RA, Savino PJ, Bernardi B, Bosley TM, Sergott RC. Hemifacial spasm: evaluation by magnetic resonance imaging and magnetic resonance tomographic angiography. Ann Neurol 1772;32:502-506
Hemifacial spasm (HFS) is characterized by unilateral involuntary contractions of seventh cranial nerve (CN VII) innervated muscles. Traditionally, the majority of HFS cases have been thought to be idiopathic. Occasional cases are associated with extraaxial mass lesions compressing CN VII or the brainstem [l, 2) and intraparenchymal lesions, including multiple sclerosis [31. Although still somewhat controversial {4},the concept of vascular compression of CN VII at the root entry zone (REZ) has been proposed as a cause based on direct visualization and relief of HFS by decompressive surgery [5-7). Neuropathological [S} and electrophysiological [9} studies of the facial nerve appear to support compression as a cause. Recent studies have attempted to correlate HFS with vascular anomalies seen neuroradiologically . A computed tomographic (CT) scan study demonstrated ipsilateral vertebrobasilar artery dolichoectasia in 33 of 46 (72%) patients [lo}.Birbamer and colleagues [l I } used magnetic resonance angiography (MRA) to identify abnormal vascular loops in 12 of 14 (86%)patients with HFS. We have used a combination of magnetic resonance imaging (MRI), gadolinium-enhanced MRI (GAD-
MRI), and MRA to evaluate HFS in an age-matched, controlled study. In addition, we have used and described the new technique of magnetic resonance tomographic angiography (MRTA) to visualize the relationship between vascular structures and both the cranial nerves and the brainstem.
From the Departments of *Neurology and $Ophthalmology, Graduate Hospital, tDepartment of Radiology, Children's Hospital of Philand 'INe~o-OPhthalrnologyService, Eye Hospital, Philadelphi%PA, and §OsPedale Italy'
Received Nov 22, 1991, and in revised form Mar 16, 1992. Accepted for publication Mar 16, 1992. Address correspondence Dr Adler, Department of Neurology, Mayo Clinic Sconsdde, 13400 E. Shes Boulevard, Scottsdale, A7, 85259.
502
Methods Patients Thirty-seven patients with HFS and 16 control patients with other neurological disorders (parkinsonism,5 patients; essential tremor, 2; progressive supranuclear palsy, 1; hand dyskinesia, 1; epilepsy, I; Creutzfeldt-Jakob disease, 1; 111 nerve palsy, 1; vertigo, 1; neurofibromatosis, 1; headache, 1; and facial pain, l), seen at Wills Eye and Graduate Hospitals (Philadelphia, PA), were imaged. The control patients were chosen from the general patient population if the exam did not reveal facial dyskinesias or clinical evidence of a cerebellopontine angle lesion. Patient characteristics including sex, age, side of HFS, and duration of HFS are listed in Table 1.
scans MRI studies were performed on a Siemens Magnetom SP 1.5-T unit. All patients had sagittal T1-weighted images (TR, 600 msec; TE, 30 msec), axial T1, intermediate (TR, 3,000
Copyright 0 1772 by the American Neurological Association
Table I. Comparison of Hemifacial Spasm and Control Patients
Patients (n) Age ( v ) " Mean SD Range Sex (%)b Male Female Side of HFS (%) Left Right Duration (yr) Mean SD Range
*
*
Hemifacial Spasm
Control
37
16
61 & 12
61
34-83
25-79
* 16
15 (41) 22 (59)
...
... 7.7 2 8.2 0.5-38
...
'p > 0.2, Student's I test. bp = 0.37, Fisher's exact test. HFS = hemifacial spasm.
msec; "E, 30 msec) and T2-weighted images (TR, 3,000 msec; TE, 80 msec), and GAD-diethylenetriamine pentaacetic acid enhanced TI-weighted images. Three-dimensional (3D) MRA was performed with TR = 40 msec, TE = 7 msec, and flip angle = 25 degrees 1121. Matrix size for MRA was 256 x 256, number of acquisitions was 1, volume size was 64 mm, each slice thickness was 1 mm, and number of partitions was 64. The MRA studies used time of flight (TOF) techniques with multiplanar reconstructions 12, 131. This technique uses saturation pulses that suppress the signal arising from the brain tissue so that the blood vessels with fast flow appear as areas of higher signal intensity. The MRA data was then reviewed both as a compressed angiographic data set using maximum intensity projection (MIP), as individual slices, and as coronally to sagitally rotated MIP images after segmentation out of all but the vertebrobasilar vascular system. In addition, using computer reconstruction, axially acquired angiographic sections were reformatted into submillimeter coronal MR images to create coronal MRTAs. The advantage of the 3D TOF MRA is that the background is still seen well enough that it can be reformatted from the original data acquisition (64 1-mm sections) into submillimeter coronal, sagittal, and oblique sections. By adjusting the window width and level of the MR console, the interface between the brain tissue and cranial nerves with the arteries can be demonstrated. Image processing was performed on a separate console and required an additional 10 minutes per case for segmentation of MRA images and coronally reconstructed MRTA. Two neuroradiologists (R.A.Z., B.B.), masked to the patient's diagnoses, independently evaluated each MR study. They determined whether there were parenchymal abnormalities, vessel tortuosity, or vascular compression of either C N VII or the pons, using all scan types. T2-weighted MRIs were used to determine the extent of intraparenchymal and extraaxial lesions, with GAD-MRI used to aid detection of mass lesions. Coronal angiotomes were scored as positive
(specifying the side of vascular compression and the offending vessel) or negative. If vessel tortuosity (by MRA) was noted without definite compression of CN VII or the pons, the MRA was considered positive but the coronal angiotome negative. Student's t test, x2 analysis, and Fisher's exact test were used for statistical analysis.
Results There was no significant difference in age or sex distribution between the control patients and patients with HFS (see Table 1). HFS was evenly distributed between left-sided (n = 18) and right-sided (n = 19) symptoms, and the mean duration of HFS was 7.7 years (see Table 1). Nonspecific high signal intensity white matter lesions, on axial T2-weighted images, in the cerebral hemispheres alone or brainstem and hemispheres were found in 10 of 16 (62.5%) control patients and 24 of 37 (64.9%) patients with HFS (p = 0.81) (Table 2). These lesions are most consistent with small vessel infarctions and did not appear to relate to the clinical findings in any of the patients. Two patients with HFS had supratentorial meningiomas detected on T2weighted and GAD-MRI images (Table 2), which appear unrelated to the HFS. Axial MRI revealed vertebrobasilar tortuosity in 5 of 16 (31%) of the control patients and 19 of 37 (51%) of the patients with HFS ( p > 0.2) (see Table 2). M U alone revealed tortuous vessels in 6 of 16 (37.5%) control patients and 24 of 37 (64.8%) patients Table 2. Abnormalities Found on MRI, MRA, and Coronal M R T A No. of Patients (%) ~
HFS"
Controlb
14 (38) 10 (27) 2 (6) 19 (51) 24 (65) 22 (59) 27 (73) 24 (65)
7 (44) 3 (19) 0 5 (31) 6 (38)
~
Axial T2-weighted image' Hemispheric only Brainstem and hemispheric GAD-enhanced MRId Vascular tortuosity, MRIe Vascular tortuosity, MRAf Ipsilateral to HFS Vascular compression, MRTAg Ipsilateral to HFS
...
1 (6)
...
"Hemifacial spasm patients (n = 37). bNeurological control patients (n = 16). 'Nonspecific, high signal intensity white matter lesions; p = 0.81, x2 analysis. dGadolinium-diethylenetriamine pentaacetic acid enhanced T1weighted MRI. ep
> 0.2.
5 > 0.05.
gp < 0.001.
MRI
= magnetic resonance imaging; MRA = magnetic resonance angiography; MRTA = magnetic resonance tomographic angiography; HFS = hemifacial spasm; GAD = gadolinium.
Adler et al: MR Study of Hemifacial Spasm 503
A
Fig 1 . Comparison of a normal magnetic monance angiogram (MRA) of the vertebrobasilar system to that of a patient with kfi-si&d hemifacial spasm (HFS). (A)Coronally displayed M R A segmented for the vertebrobasilar system shows the larger
ldt vertebral artery (white arrowhead),
with a smaller right vertebral artery giving rise to the basilar artery. Note that the basilar artery is midline. The right vertebral artery gives rise t o a dominant posterior inferior cerebellar artery (PICA) (open arrow). The basilar artery gives rise to a dominant lt$ anterior inferior cerebellar artery (AKA) (arrow). There is no k$t PICA or right AKA. (B) A patient with lejl HFS has a dominant ldt vertebral artery that is ectatic with elongation at the point of origin of a dominant le$t PICA (arrow). Compression ofthe seventh cranial nerve (not visualized) in this patient occurred at this site.
with HFS ( p > 0.05) (Fig 1; Table 2). The tortuosity was ipsilateral to the HFS in 22 of 24 (91.6%) of the patients with HFS. Coronal MRTA revealed definite compression of C N VII or the brainstem in only 1 of 16 (6.3%) control and 27 of 37 (73.0%) patients with HFS ( p < 0.001) (Figs 2, 3, Table 2). The MRI, MRA, and coronal MRTA vascular abnormalities were in the same 27 patients with HFS. No patient with HFS had an abnormality on MRI or M U , and not on MRTA. Only 1 control patient with MRI or MRA vessel tortuosity had compression on MRTA. The control patient had parkinsonism. N o compression was found in 15 of 16 (93.8%) control patients and 10 of 37 (27.0%) patients with HFS. Vascular compression, on coronal MRTA, was ipsilateral to the HFS in 24 of 27 (88.9%) patients, and contralateral to the HFS in 3 of 27 (11.1%) patients. 504 Annals of Neurology Vol 32 No 4 October 1992
B
Overall, 24 of 37 (64.9%) patients with HFS had ipsilateral vascular compression. The vertebral artery was the compressing artery in the majority of patients (58.3%), with the basilar (16.7%), anterior inferior cerebellar (16.7%), and posterior inferior cerebellar (8.3%) arteries also implicated. Determination of which artery was compressing CN VII or the brainstem required the combined evaluation of the MRA, axially acquired angiographic sections, and coronal MRTA. Discussion Using MRI, MRA, and MRTA, we have demonstrated ipsilateral vascular compression of C N VII or the pons in 24 of 37 (64.9%) patients with HFS, whereas only 1 of 16 (6.3%) neurological control patients had compression. The theory that vascular compression of CN VII can lead to HFS has been supported by direct visualization at the time of surgery C4-91, symptomatic response to vascular decompression 14-91, neuropathological C81, and neurophysiological [91 findings. A similar mechanism has also been proposed for other cranial nerve hyperactivity syndromes C141. Some arguments opposing this mechanism include the lack of bilaterality of symptoms, the absence of the various cranial nerve hyperactivity syndromes occurring simultaneously, and the role of traumatizing the cranial nerve at the time of decompression C41. Noninvasive neuroradiological techniques have allowed evaluation of vasculadparenchymal relationships. Head CT scans with contrast revealed dolichoec-
A
A
A Fig 2. Patient with le~5themifacial spasm and compression of the ldt seventh cranial nerve (CN VII) by basilar artery ectasia. (A)Axial 1-mm time of flight magnetic resonance (MR) angiographic section shows the basikar artery within the left cerebellopontineangle (CPA) compresses CN VII (arrow). (B) Coronal 0.9-mmMR tomographic angiogram (MRTA) section obtained from reformatting the axially acquired MR angiographic dzta. This i m g e shows that the high signal intensity basilar artery (arrowhead) focally elevates and compresses CN VII (arrow).
tasia of the vertebrobasilar artery in 36 of 46 (78%) patients [lo}. The convexity was ipsilateral to the HFS in 33 of 36 and contralateral in 3 of 36. Thus, 33 of 46 (72%) patients had ipsilateral dolichoectasia, consistent with our findings. In a separate CT study, by the same group, none of the control patients (n = 126) had the vertebrobasilar artery in the cerebellopontine angle (CPA) [15). In contrast, a third study found only 3 of 50 (6%) patients with HFS had the vertebrobasilar artery seen in the CPA by CT scan, despite finding vascular compression of C N VII at the time of surgical decompression in all 50 patients { 161. Angiographic
B Fig 3. Patient with left hemifacial spasm and an ectatic lefit vertebral and basilar artery compressing the lefit seventh cranial nerve (CN VII). (A)Axial 1-mm magnetic resonance ( M R ) angiographic section shows the basikar artery lies in the lefit cerebellopontine angle contacting CN VII (arrow) as it enters the internal auditory canal. (B) Coronal reformatted 0.9-mmM R tomographic angiographic section shows the basilar artery lies at the pars acustica of the lefit internal auditory canal indenting the left side of the pons (arrowhead).
analysis of these 50 patients revealed that 70% had anomalies of the vertebrobasilar system [16}. Neither the CT scan nor the angiographic studies specifically detected compression of either C N VII or the pons; they only detected ectasia or malposition of the artery. Recent studies have used MR technology to evaluate HFS. The first, using M U , found that 12 of 14 (86%) patients with HFS had abnormal vascular loops ipsilaterally 1111. This study was not controlled and did not visualize the relationship between blood vessel and paAdler et d: MR Study of Hemifacial Spasm 505
renchyma. In another study, using MRI without angiography, ipsilateral abnormal vascular loops compressing CN VII at the RE2 were found in all 13 patients with HFS f171. In addition, 22% of the 70 controls also had asymptomatic vascular contact of the C N VII RE2 with only 1% having true compression C171. These studies show a greater percentage of anomalies than our data. Our study first shows that nonspecific high signal intensity lesions on T2-weighted images are frequently found in patients with HFS and other neurological disorders. These findings appear to be unrelated to the HFS. Second, GAD-MRI did not add any information to the noncontrast MRI data. Both studies demonstrated two unsuspected, supratentorial, extraaxial m s lesions, thought to be clinically insignificant meningiomas. The review by Digre and Corbett f31, of 1,688 published cases of HFS, revealed only 19 cases of extraaxial tumor as a cause for HFS, whereas Janetta f14J found only 3 tumors in 229 patients. Unsuspected tumors were found in 2 of 46 patients with HFS in a contrast-enhanced CT scan study [lo]. Because noncontrast MRI identifies mass lesions very well, and the incidence of these lesions in HFS is low, it is unlikely that GAD-MRI adds much to the diagnostic capabilities of noncontrast MRI in this disorder. The presence of vascular tortuosity and vascular compression was significantly higher in the patients with HFS compared with control patients. Because controls were age-matched, it is unlikely that aging alone results in brain ‘‘saeng” El41 and vascular compression syndromes; rather this appears to be a specific pathophysiological disturbance. Yet, 10 patients with HFS had no vascular compression, 3 patients with HFS had contralateral compression, and one control patient had compression. This suggests that vascular compression may not be the cause of HFS in these 10 patients, although an alternative cause was not demonstrated. In addition, the presence of compression does not always predict clinical symptomatology. A few cases of venous compression have been identified at surgery f 141, but MRI, MRA, and MRTA do not adequately image venous structures. MRI appears to be superior to CT scanning in evaluating HFS. CT scans have poor posterior fossa resolution, rarely visuahe CN VII, and poorly determine vascular interactions with parenchyma. Conventional cerebral angiography can determine vascular anomalies without showing their relationship to the brain parenchyma or cranial nerves, and there is occasional morbidity and mortality. MRI alone was able to detect vascular tortuosity, yet it was not as sensitive or specific as MRTA. MRA alone, although more sensitive than
506 Annals of Neurology Vol 32 No 4
October 1992
MRI, was less sensitive and specific than MRTA in determining vascular tortuosity, and lacks the capability to establish a blood VesseUparenchyrna interaction. MRTA is thus the most accurate, noninvasive imaging technique available for establishing vascular compression in patients with HFS. Our study supports vascular compression as the cause of HFS in some patients, although pathological or surgical confirmation is lacking. This is the first study we are aware of using the MRTA technique, and demonstrates its value in evaluating vascular compression syndromes and vascularhsue interactions. We recommend MRI combined with MRTA as a noninvasive method to fully evaluate patients with HFS. References 1. Sprik C, Wirtschafter JD. Hemifacial spasm due to intracranial tumor: an international survey of botulinum toxin investigators. Ophthalmology 1988;95:1042-1045 2. Weiner WJ, Lang AE. Movement disorders: a comprehensive survey. Mount Kisco, New York: Futura Publishing, 1989: 5 10-5 14 3. Digre K, Corbett JJ. Hemifacial spasm: differential diagnosis, mechanism, and treatment. Adv Neurol 1988;49:151-176 4. Adams CBT. Microvascular compression: an alternative view and hypothesis. J Neurosurg 1989;57:1-12 5. Gardner WT, Sava GA. Hemifacial spasm: a reversible pathophysiologic state. J Neurosurg 1962;19:240-247 6. Janetta PJ, Abbasy M, Maroon JC, et al. Etiology and definitive microsurgical treatment of hemifacial spasm: operative techniques and results in 47 patients. J Neurosurg 1977;47:321-328 7. Auger RG, Piepgras DG, Laws ER. Hemifacial spasm: results of microvascular decompression of the facial nerve in 54 patients. Mayo Clin Proc 1986;61:640-644 8. Coad JE, Wirtschafter JD, Haines SJ, et al. Familial hemifacial spasm associated with arterial compression of the facial nerve: case report. J Neurosurg 1991;74:290-296 9. Nielsen VK, Janetta PJ. Pathophysiology of hemifacial spasm: 111. Effects of facial nerve decompression. Neurology 1984; 341891497 10. Digre KB, Corbett JJ, Smoker WRK, McKusker S. CT and hemifacial spasm. Neurology 1988;38:1111-1113 11. Birbamer G, Felber S, Poewe W, et al. MR-angiography--a new noninvasive approach in diagnosis of hemifacial spasm. Mov Disord 1990;5(suppl 1):69 (Abstract) 12. Zimmerman RA, Bogdan AR, Gusnard DA. Pediatric magnetic resonance angiography: assessment of stroke. Cardiovasc Intervent Radio1 1992;15:60-64 13. Masaryk TJ, Modic MT, Ross JS, et al. Intracranial circulation: preliminary clinical results with three-dimensional (volume) MR angiography. Radiology 1989;17 1:793-799 14. Janetta PJ. Neurovascular compression in cranial nerve and systemic disease. Ann Surg 1990;192:5 18-525 15. Smoker WRK, Price MJ, Keyes WD, et al. High-resolution computed tomography of the basilar artery. I. Normal size and position. Am J Neuroradiol 1986;7:55-60 16. Carlos R, Fukui M, Hasuo K, et al. Radiological analysis of hemifacial spasm with special reference to angiographicmanifestations. Neuroradiology 1986;28:288-295 17. Tash R, DeMeritt J, Sze G, Leslie D. Hemifacial spasm: MR imaging features. Am J Neuroradiol 1991;12:839-842
We evaluated 37 patients with hemifacial spasm and 16 age-matched control patients with other neurological disorders using magnetic resonance (MR) imaging, MR angiography, and MR tomographic angiography. MR tomographic angiography is a new technique using computer reconstruction of MR angiographic images to create coronal angiotomes that display tissue and arterial structures on the same image. Twenty-four of 37 (64.9%)patients with hemifacial spasm had ipsilateral vascular compression of cranial nerve VII or the pons noted by this technique, whereas only I of 16 (6.3%)control patients had compression. MR imaging and MR angiography were less sensitive and less specific in evaluating for vascular compression. This study supports vascular compression of cranial nerve VII or the pons as a cause of hemifacial spasm, and demonstrates MR tomographic angiography's value as an excellent, noninvasive technique to demonstrate the compression. Adler CH, Zimrnerman RA, Savino PJ, Bernardi B, Bosley TM, Sergott RC. Hemifacial spasm: evaluation by magnetic resonance imaging and magnetic resonance tomographic angiography. Ann Neurol 1772;32:502-506
Hemifacial spasm (HFS) is characterized by unilateral involuntary contractions of seventh cranial nerve (CN VII) innervated muscles. Traditionally, the majority of HFS cases have been thought to be idiopathic. Occasional cases are associated with extraaxial mass lesions compressing CN VII or the brainstem [l, 2) and intraparenchymal lesions, including multiple sclerosis [31. Although still somewhat controversial {4},the concept of vascular compression of CN VII at the root entry zone (REZ) has been proposed as a cause based on direct visualization and relief of HFS by decompressive surgery [5-7). Neuropathological [S} and electrophysiological [9} studies of the facial nerve appear to support compression as a cause. Recent studies have attempted to correlate HFS with vascular anomalies seen neuroradiologically . A computed tomographic (CT) scan study demonstrated ipsilateral vertebrobasilar artery dolichoectasia in 33 of 46 (72%) patients [lo}.Birbamer and colleagues [l I } used magnetic resonance angiography (MRA) to identify abnormal vascular loops in 12 of 14 (86%)patients with HFS. We have used a combination of magnetic resonance imaging (MRI), gadolinium-enhanced MRI (GAD-
MRI), and MRA to evaluate HFS in an age-matched, controlled study. In addition, we have used and described the new technique of magnetic resonance tomographic angiography (MRTA) to visualize the relationship between vascular structures and both the cranial nerves and the brainstem.
From the Departments of *Neurology and $Ophthalmology, Graduate Hospital, tDepartment of Radiology, Children's Hospital of Philand 'INe~o-OPhthalrnologyService, Eye Hospital, Philadelphi%PA, and §OsPedale Italy'
Received Nov 22, 1991, and in revised form Mar 16, 1992. Accepted for publication Mar 16, 1992. Address correspondence Dr Adler, Department of Neurology, Mayo Clinic Sconsdde, 13400 E. Shes Boulevard, Scottsdale, A7, 85259.
502
Methods Patients Thirty-seven patients with HFS and 16 control patients with other neurological disorders (parkinsonism,5 patients; essential tremor, 2; progressive supranuclear palsy, 1; hand dyskinesia, 1; epilepsy, I; Creutzfeldt-Jakob disease, 1; 111 nerve palsy, 1; vertigo, 1; neurofibromatosis, 1; headache, 1; and facial pain, l), seen at Wills Eye and Graduate Hospitals (Philadelphia, PA), were imaged. The control patients were chosen from the general patient population if the exam did not reveal facial dyskinesias or clinical evidence of a cerebellopontine angle lesion. Patient characteristics including sex, age, side of HFS, and duration of HFS are listed in Table 1.
scans MRI studies were performed on a Siemens Magnetom SP 1.5-T unit. All patients had sagittal T1-weighted images (TR, 600 msec; TE, 30 msec), axial T1, intermediate (TR, 3,000
Copyright 0 1772 by the American Neurological Association
Table I. Comparison of Hemifacial Spasm and Control Patients
Patients (n) Age ( v ) " Mean SD Range Sex (%)b Male Female Side of HFS (%) Left Right Duration (yr) Mean SD Range
*
*
Hemifacial Spasm
Control
37
16
61 & 12
61
34-83
25-79
* 16
15 (41) 22 (59)
...
... 7.7 2 8.2 0.5-38
...
'p > 0.2, Student's I test. bp = 0.37, Fisher's exact test. HFS = hemifacial spasm.
msec; "E, 30 msec) and T2-weighted images (TR, 3,000 msec; TE, 80 msec), and GAD-diethylenetriamine pentaacetic acid enhanced TI-weighted images. Three-dimensional (3D) MRA was performed with TR = 40 msec, TE = 7 msec, and flip angle = 25 degrees 1121. Matrix size for MRA was 256 x 256, number of acquisitions was 1, volume size was 64 mm, each slice thickness was 1 mm, and number of partitions was 64. The MRA studies used time of flight (TOF) techniques with multiplanar reconstructions 12, 131. This technique uses saturation pulses that suppress the signal arising from the brain tissue so that the blood vessels with fast flow appear as areas of higher signal intensity. The MRA data was then reviewed both as a compressed angiographic data set using maximum intensity projection (MIP), as individual slices, and as coronally to sagitally rotated MIP images after segmentation out of all but the vertebrobasilar vascular system. In addition, using computer reconstruction, axially acquired angiographic sections were reformatted into submillimeter coronal MR images to create coronal MRTAs. The advantage of the 3D TOF MRA is that the background is still seen well enough that it can be reformatted from the original data acquisition (64 1-mm sections) into submillimeter coronal, sagittal, and oblique sections. By adjusting the window width and level of the MR console, the interface between the brain tissue and cranial nerves with the arteries can be demonstrated. Image processing was performed on a separate console and required an additional 10 minutes per case for segmentation of MRA images and coronally reconstructed MRTA. Two neuroradiologists (R.A.Z., B.B.), masked to the patient's diagnoses, independently evaluated each MR study. They determined whether there were parenchymal abnormalities, vessel tortuosity, or vascular compression of either C N VII or the pons, using all scan types. T2-weighted MRIs were used to determine the extent of intraparenchymal and extraaxial lesions, with GAD-MRI used to aid detection of mass lesions. Coronal angiotomes were scored as positive
(specifying the side of vascular compression and the offending vessel) or negative. If vessel tortuosity (by MRA) was noted without definite compression of CN VII or the pons, the MRA was considered positive but the coronal angiotome negative. Student's t test, x2 analysis, and Fisher's exact test were used for statistical analysis.
Results There was no significant difference in age or sex distribution between the control patients and patients with HFS (see Table 1). HFS was evenly distributed between left-sided (n = 18) and right-sided (n = 19) symptoms, and the mean duration of HFS was 7.7 years (see Table 1). Nonspecific high signal intensity white matter lesions, on axial T2-weighted images, in the cerebral hemispheres alone or brainstem and hemispheres were found in 10 of 16 (62.5%) control patients and 24 of 37 (64.9%) patients with HFS (p = 0.81) (Table 2). These lesions are most consistent with small vessel infarctions and did not appear to relate to the clinical findings in any of the patients. Two patients with HFS had supratentorial meningiomas detected on T2weighted and GAD-MRI images (Table 2), which appear unrelated to the HFS. Axial MRI revealed vertebrobasilar tortuosity in 5 of 16 (31%) of the control patients and 19 of 37 (51%) of the patients with HFS ( p > 0.2) (see Table 2). M U alone revealed tortuous vessels in 6 of 16 (37.5%) control patients and 24 of 37 (64.8%) patients Table 2. Abnormalities Found on MRI, MRA, and Coronal M R T A No. of Patients (%) ~
HFS"
Controlb
14 (38) 10 (27) 2 (6) 19 (51) 24 (65) 22 (59) 27 (73) 24 (65)
7 (44) 3 (19) 0 5 (31) 6 (38)
~
Axial T2-weighted image' Hemispheric only Brainstem and hemispheric GAD-enhanced MRId Vascular tortuosity, MRIe Vascular tortuosity, MRAf Ipsilateral to HFS Vascular compression, MRTAg Ipsilateral to HFS
...
1 (6)
...
"Hemifacial spasm patients (n = 37). bNeurological control patients (n = 16). 'Nonspecific, high signal intensity white matter lesions; p = 0.81, x2 analysis. dGadolinium-diethylenetriamine pentaacetic acid enhanced T1weighted MRI. ep
> 0.2.
5 > 0.05.
gp < 0.001.
MRI
= magnetic resonance imaging; MRA = magnetic resonance angiography; MRTA = magnetic resonance tomographic angiography; HFS = hemifacial spasm; GAD = gadolinium.
Adler et al: MR Study of Hemifacial Spasm 503
A
Fig 1 . Comparison of a normal magnetic monance angiogram (MRA) of the vertebrobasilar system to that of a patient with kfi-si&d hemifacial spasm (HFS). (A)Coronally displayed M R A segmented for the vertebrobasilar system shows the larger
ldt vertebral artery (white arrowhead),
with a smaller right vertebral artery giving rise to the basilar artery. Note that the basilar artery is midline. The right vertebral artery gives rise t o a dominant posterior inferior cerebellar artery (PICA) (open arrow). The basilar artery gives rise to a dominant lt$ anterior inferior cerebellar artery (AKA) (arrow). There is no k$t PICA or right AKA. (B) A patient with lejl HFS has a dominant ldt vertebral artery that is ectatic with elongation at the point of origin of a dominant le$t PICA (arrow). Compression ofthe seventh cranial nerve (not visualized) in this patient occurred at this site.
with HFS ( p > 0.05) (Fig 1; Table 2). The tortuosity was ipsilateral to the HFS in 22 of 24 (91.6%) of the patients with HFS. Coronal MRTA revealed definite compression of C N VII or the brainstem in only 1 of 16 (6.3%) control and 27 of 37 (73.0%) patients with HFS ( p < 0.001) (Figs 2, 3, Table 2). The MRI, MRA, and coronal MRTA vascular abnormalities were in the same 27 patients with HFS. No patient with HFS had an abnormality on MRI or M U , and not on MRTA. Only 1 control patient with MRI or MRA vessel tortuosity had compression on MRTA. The control patient had parkinsonism. N o compression was found in 15 of 16 (93.8%) control patients and 10 of 37 (27.0%) patients with HFS. Vascular compression, on coronal MRTA, was ipsilateral to the HFS in 24 of 27 (88.9%) patients, and contralateral to the HFS in 3 of 27 (11.1%) patients. 504 Annals of Neurology Vol 32 No 4 October 1992
B
Overall, 24 of 37 (64.9%) patients with HFS had ipsilateral vascular compression. The vertebral artery was the compressing artery in the majority of patients (58.3%), with the basilar (16.7%), anterior inferior cerebellar (16.7%), and posterior inferior cerebellar (8.3%) arteries also implicated. Determination of which artery was compressing CN VII or the brainstem required the combined evaluation of the MRA, axially acquired angiographic sections, and coronal MRTA. Discussion Using MRI, MRA, and MRTA, we have demonstrated ipsilateral vascular compression of C N VII or the pons in 24 of 37 (64.9%) patients with HFS, whereas only 1 of 16 (6.3%) neurological control patients had compression. The theory that vascular compression of CN VII can lead to HFS has been supported by direct visualization at the time of surgery C4-91, symptomatic response to vascular decompression 14-91, neuropathological C81, and neurophysiological [91 findings. A similar mechanism has also been proposed for other cranial nerve hyperactivity syndromes C141. Some arguments opposing this mechanism include the lack of bilaterality of symptoms, the absence of the various cranial nerve hyperactivity syndromes occurring simultaneously, and the role of traumatizing the cranial nerve at the time of decompression C41. Noninvasive neuroradiological techniques have allowed evaluation of vasculadparenchymal relationships. Head CT scans with contrast revealed dolichoec-
A
A
A Fig 2. Patient with le~5themifacial spasm and compression of the ldt seventh cranial nerve (CN VII) by basilar artery ectasia. (A)Axial 1-mm time of flight magnetic resonance (MR) angiographic section shows the basikar artery within the left cerebellopontineangle (CPA) compresses CN VII (arrow). (B) Coronal 0.9-mmMR tomographic angiogram (MRTA) section obtained from reformatting the axially acquired MR angiographic dzta. This i m g e shows that the high signal intensity basilar artery (arrowhead) focally elevates and compresses CN VII (arrow).
tasia of the vertebrobasilar artery in 36 of 46 (78%) patients [lo}. The convexity was ipsilateral to the HFS in 33 of 36 and contralateral in 3 of 36. Thus, 33 of 46 (72%) patients had ipsilateral dolichoectasia, consistent with our findings. In a separate CT study, by the same group, none of the control patients (n = 126) had the vertebrobasilar artery in the cerebellopontine angle (CPA) [15). In contrast, a third study found only 3 of 50 (6%) patients with HFS had the vertebrobasilar artery seen in the CPA by CT scan, despite finding vascular compression of C N VII at the time of surgical decompression in all 50 patients { 161. Angiographic
B Fig 3. Patient with left hemifacial spasm and an ectatic lefit vertebral and basilar artery compressing the lefit seventh cranial nerve (CN VII). (A)Axial 1-mm magnetic resonance ( M R ) angiographic section shows the basikar artery lies in the lefit cerebellopontine angle contacting CN VII (arrow) as it enters the internal auditory canal. (B) Coronal reformatted 0.9-mmM R tomographic angiographic section shows the basilar artery lies at the pars acustica of the lefit internal auditory canal indenting the left side of the pons (arrowhead).
analysis of these 50 patients revealed that 70% had anomalies of the vertebrobasilar system [16}. Neither the CT scan nor the angiographic studies specifically detected compression of either C N VII or the pons; they only detected ectasia or malposition of the artery. Recent studies have used MR technology to evaluate HFS. The first, using M U , found that 12 of 14 (86%) patients with HFS had abnormal vascular loops ipsilaterally 1111. This study was not controlled and did not visualize the relationship between blood vessel and paAdler et d: MR Study of Hemifacial Spasm 505
renchyma. In another study, using MRI without angiography, ipsilateral abnormal vascular loops compressing CN VII at the RE2 were found in all 13 patients with HFS f171. In addition, 22% of the 70 controls also had asymptomatic vascular contact of the C N VII RE2 with only 1% having true compression C171. These studies show a greater percentage of anomalies than our data. Our study first shows that nonspecific high signal intensity lesions on T2-weighted images are frequently found in patients with HFS and other neurological disorders. These findings appear to be unrelated to the HFS. Second, GAD-MRI did not add any information to the noncontrast MRI data. Both studies demonstrated two unsuspected, supratentorial, extraaxial m s lesions, thought to be clinically insignificant meningiomas. The review by Digre and Corbett f31, of 1,688 published cases of HFS, revealed only 19 cases of extraaxial tumor as a cause for HFS, whereas Janetta f14J found only 3 tumors in 229 patients. Unsuspected tumors were found in 2 of 46 patients with HFS in a contrast-enhanced CT scan study [lo]. Because noncontrast MRI identifies mass lesions very well, and the incidence of these lesions in HFS is low, it is unlikely that GAD-MRI adds much to the diagnostic capabilities of noncontrast MRI in this disorder. The presence of vascular tortuosity and vascular compression was significantly higher in the patients with HFS compared with control patients. Because controls were age-matched, it is unlikely that aging alone results in brain ‘‘saeng” El41 and vascular compression syndromes; rather this appears to be a specific pathophysiological disturbance. Yet, 10 patients with HFS had no vascular compression, 3 patients with HFS had contralateral compression, and one control patient had compression. This suggests that vascular compression may not be the cause of HFS in these 10 patients, although an alternative cause was not demonstrated. In addition, the presence of compression does not always predict clinical symptomatology. A few cases of venous compression have been identified at surgery f 141, but MRI, MRA, and MRTA do not adequately image venous structures. MRI appears to be superior to CT scanning in evaluating HFS. CT scans have poor posterior fossa resolution, rarely visuahe CN VII, and poorly determine vascular interactions with parenchyma. Conventional cerebral angiography can determine vascular anomalies without showing their relationship to the brain parenchyma or cranial nerves, and there is occasional morbidity and mortality. MRI alone was able to detect vascular tortuosity, yet it was not as sensitive or specific as MRTA. MRA alone, although more sensitive than
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MRI, was less sensitive and specific than MRTA in determining vascular tortuosity, and lacks the capability to establish a blood VesseUparenchyrna interaction. MRTA is thus the most accurate, noninvasive imaging technique available for establishing vascular compression in patients with HFS. Our study supports vascular compression as the cause of HFS in some patients, although pathological or surgical confirmation is lacking. This is the first study we are aware of using the MRTA technique, and demonstrates its value in evaluating vascular compression syndromes and vascularhsue interactions. We recommend MRI combined with MRTA as a noninvasive method to fully evaluate patients with HFS. References 1. Sprik C, Wirtschafter JD. Hemifacial spasm due to intracranial tumor: an international survey of botulinum toxin investigators. Ophthalmology 1988;95:1042-1045 2. Weiner WJ, Lang AE. Movement disorders: a comprehensive survey. Mount Kisco, New York: Futura Publishing, 1989: 5 10-5 14 3. Digre K, Corbett JJ. Hemifacial spasm: differential diagnosis, mechanism, and treatment. Adv Neurol 1988;49:151-176 4. Adams CBT. Microvascular compression: an alternative view and hypothesis. J Neurosurg 1989;57:1-12 5. Gardner WT, Sava GA. Hemifacial spasm: a reversible pathophysiologic state. J Neurosurg 1962;19:240-247 6. Janetta PJ, Abbasy M, Maroon JC, et al. Etiology and definitive microsurgical treatment of hemifacial spasm: operative techniques and results in 47 patients. J Neurosurg 1977;47:321-328 7. Auger RG, Piepgras DG, Laws ER. Hemifacial spasm: results of microvascular decompression of the facial nerve in 54 patients. Mayo Clin Proc 1986;61:640-644 8. Coad JE, Wirtschafter JD, Haines SJ, et al. Familial hemifacial spasm associated with arterial compression of the facial nerve: case report. J Neurosurg 1991;74:290-296 9. Nielsen VK, Janetta PJ. Pathophysiology of hemifacial spasm: 111. Effects of facial nerve decompression. Neurology 1984; 341891497 10. Digre KB, Corbett JJ, Smoker WRK, McKusker S. CT and hemifacial spasm. Neurology 1988;38:1111-1113 11. Birbamer G, Felber S, Poewe W, et al. MR-angiography--a new noninvasive approach in diagnosis of hemifacial spasm. Mov Disord 1990;5(suppl 1):69 (Abstract) 12. Zimmerman RA, Bogdan AR, Gusnard DA. Pediatric magnetic resonance angiography: assessment of stroke. Cardiovasc Intervent Radio1 1992;15:60-64 13. Masaryk TJ, Modic MT, Ross JS, et al. Intracranial circulation: preliminary clinical results with three-dimensional (volume) MR angiography. Radiology 1989;17 1:793-799 14. Janetta PJ. Neurovascular compression in cranial nerve and systemic disease. Ann Surg 1990;192:5 18-525 15. Smoker WRK, Price MJ, Keyes WD, et al. High-resolution computed tomography of the basilar artery. I. Normal size and position. Am J Neuroradiol 1986;7:55-60 16. Carlos R, Fukui M, Hasuo K, et al. Radiological analysis of hemifacial spasm with special reference to angiographicmanifestations. Neuroradiology 1986;28:288-295 17. Tash R, DeMeritt J, Sze G, Leslie D. Hemifacial spasm: MR imaging features. Am J Neuroradiol 1991;12:839-842
