The Neuroradiology Journal 21: 101-106, 2008
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Morphological MRI and 3D Myelocisternography MRI in Spontaneous Intracranial Hypotension A Report of Four Cases F.A. LUPO, A. PALADINI, G. STICCHI, P. LUPO Neuroradiology Unit, Lecce Health Trust, “V. Fazzi” Hospital; Lecce, Italy
Key words: intracranial hypotension, postural headache, spontaneous subdural collection, pituitary swelling
SUMMARY – Spontaneous intracranial hypotension (SIH) is a polyhedric syndrome whose common denominator is postural headache. We describe four cases of spontaneous intracranial hypotension, their clinical-iconographic aspects, and emphasize the use of morphological MRI in the diagnosis and follow-up of this condition. In addition, we propose 3D myelocisternography MRI as a further contribution in cerebrospinal fluid losses causing postural headache.
Introduction Spontaneous intracranial hypotension (SIH), first described by Schaltenbrandt in 1938 19, is a syndrome characterized by a spontaneous reduction of cerebrospinal fluid pressure in the absence of trauma, surgery or lumbar puncture, and can follow minor trauma, like sneezing, coughing, etc. SIH usually results from CSF loss from leakages of meningeal sheath in points of minor resistance, with consequent CSF volume and pressure reduction. The hallmark symptom of SIH is postural headache, characterized by its appearance less than 15 minutes after standing, and by its disappearance or attenuation less than 30 minutes after lying down 18. Neck stiffness, nausea, vomiting, horizontal diplopia, dizziness, photophobia, deafness, and psychomotor excitement are often associated. CSF examination can be normal or slightly impaired by elevated proteins, or lymphocytic pleiocytosis, the presence of red cells or xanthochromia. CSF pressure is low (less than 60 mm H2O) and it can be impossible to measure with lumbar punture: the so-called “ dry tap” 6. The pharmacologic management of SIH is
similar to that of headache secondary to lumbar punture and includes: bed rest, analgesics, sedatives, caffeine, hydration, blood haemostasis or epidural saline infusion 15. Intracranial and spinal cord imaging includes morphological MRI, myelography MRI and radionuclide cisternography. These techniques are suitable not only for diagnosing this syndrome, but also for excluding any organic causes responsible for impaired CSF pressure. We describe four cases of postural headache, and show correlative brain and spinal cord changes with a low field strength MRI, using morphological studies and 3D myelocisternography MRI. Material and Methods We describe four patients aged 35-60 years, average age 45 years, two men and two women, with spontaneous intracranial hypotension who underwent MRI of brain using a low-field strength Philips Gyroscan T5 Intera 0.5 T. Brain study was done in the axial plane with SE T1, DP, T2, FLAIR sequences, and then using 0.2 M i.v. paramagnetic contrast me101
Morphological MRI and 3D Myelocisternography MRI in Spontaneous Intracranial Hypotension
F.A. Lupo
➜
Figure 1 Cervical MRI SPIR T1 mdc sequence at C1-C2; (TR 62 TE 14 Flip 30): normal anatomy of cervical venous structures. 1 axis body; 2 obliquus capitis inferior muscle; 3 medulla; 4 rectus capitis major muscle; 5 parotid gland. AIVVP Anterior internal vertebral venous plexus, PIEVVP posterior internal (arrow) and external (outlined arrow) vertebral venous plexus, DCV deep cervical vein. Figure 2 Diffuse meningeal thickening.
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Figure 3 1 Pseudo-hyperplasia of pituitary gland; 2 cerebellar pseudotumor characterized by: cortical grooves smoothing, brain axis posterior surface impressio; prepontobulbar cistern volumetric reduction, initial descent of cerebellar tonsil into foramen magnu; 3 thickening of pachymeninx and internal anterior vertebral venous plexus.
dium [Gadobenate dimeglumine (Multihance - Bracco)]. Subsequently the spine was studied with SE T1 and TSE T2 axial and sagittal sequences and with sagittal fat-suppression SPIR TSE 102
T2 3D sequence, followed by axial and coronal MIP reconstructions. All patients were monitored with MRI for one to two months after onset. They also underwent lumbar punture and CSF examination.
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Case Reports Case 1: A 60-year-old man had severe orthostatic headache exacerbated by sudden standing and mitigated by bed-rest. He also had concomitant dizziness. He had no history of recent brain or spine trauma or lumbar punture. The patient did not have either fever or inflammatory index. Brain CT was negative. Brain MRI showed a diffuse thickening and a marked enhancement of the meningeal small sheath, from upper skull to vertex (figure 2), and pituitary swelling. There were no subdural flaps, or cerebellar tonsil engagement in the foramen magnum. Cervical spine MRI was negative for extradural collections, but demonstrated perimedullary dural enhancement. Lumbar punture identified a 40 mm H2O CSF pressure, without cytological abnormalities. The patient had no systemic pain, collagen disorder or vascular deficit. He gradually recovered thanks to bed-rest, anti-inflammatory drugs and bland steroids. Four months later, brain-spine MRI demonstrated a complete regression of the initial picture. Case 2: A 35-year-old man went to the emergency unit for severe headache and sudden muscle weakness. History-taking disclosed only two hours of exposure to the sun in early morning. He recalled a remote gastroresection for Crohn’s disease, now clinically and biochemically silent, so he was not receiving therapy. He had no fever, normal blood test, VES negative. Standing exacerbated his headache with horizontal diplopia. Brain and spine MRI revealed a pathological enhancement of the dura mater, and a soft fluid bilateral subdural flap to the convexity. No leakage was disclosed by myelocisternography MRI and lumbar puncture was negative. The patient improved with bed-rest, analgesics and rehydration. Six months later brain and spine MRI were normal. Case 3: A 36-year-old woman presented severe mainly occipital headache, rigor nucalis and psychomotor excitement. She was hospitalized in the infectious disease division. Symptoms had begun suddenly two days before hospitalization and were exacerbated by standing. Bed-rest attenuated but did not resolve the persistent NSAID-resistant headache. Blood tests and lumbar punture failed to disclose inflammation. CSF was mildly positive, and cytological examination showed reduced
The Neuroradiology Journal 21: 101-106, 2008
proteins. The persistence of severe headache led to administration of cortisone. Brain and total spine MRI showed a reactive diffuse encephalic and perimedullary dural thickening, cerebellar pseudotumor, characterized by cortical mantle thinning, brain axis posterior surface impression, prepontobulbar cistern volumetric reduction and initial descent of cerebellar tonsils into the foramen magnum (figure 3). Examination was completed with myelocisternography MRI, that revealed a small CSF collection in the dural sac at D11 and subsequently in the left nerve root (figure 4). History-taking failed to disclose trauma, so we confirmed the CSF drip was correlated to meningeal leakage, the stereotype of SIH 25. The patient did not respond to analgaesics, and reacted minimally to cortisone and bedrest. So doctors opted for haematic tamponade 16 . The patient initially refused the invasive therapy, but persistence of symptoms forced her to accept a blood patch. She recovered very quickly! (figure 5). Case 4: A 50-year-old woman with severe occipital headache, irresistible in orthostatism. History-taking failed to disclose trauma. The headache failed to respond to common anaegaesics and it was attenuated only with bedrest and cortisone. Brain MRI before and after i.v. contrast medium administration showed diffuse pachymeningeal thickening and pituitary swelling. MRI after four months displays normal findings: in particular there was no further meningeal irritation, and re-establishment of pituitary volume. The current clinical picture is normal and the headache has disappeared. Results We did not use alternative scans to standard brain and spine MRI sequences for SIH before and after i.v. contrast administration. However, SPIR T2 3D myelocisternography MRI with fat suppression was necessary to assess contingent meningeal leakeage. SE T1 sequences after i.v. contrast administration showed diffuse intense enhancement of the pachymeninx, and often a levelling of up– under tentorial grooves. In one of our four patients we were able to support the so-called “leakage”, with transfer of CSF into an extradural space, and dilation of the anterior peridural spinal venous plexus 6 . In all cases the pituitary gland was diffusely swollen and normal after therapy 15. 103
Morphological MRI and 3D Myelocisternography MRI in Spontaneous Intracranial Hypotension
F.A. Lupo
Figure 4 Myelography MRI: perimedullary subarachnoidal space at D11 (arrowhead); right and left radicular pouch at D11 ( small arrows); left peridural CSF collection and fistulous pathway (large arrow).
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B
C
Figure 5 A) SE Ax T1 mdc. B) Sagittal SE T1 mdc. C) Myelography. Examinations after therapy and clinical picture resolution. Note: dural thickening, cervical venous turgor and pituitary gland pseudo- hyperplasia disappearance; reduction of cerebellar impression on brain axis and re-expansion of prepontobulbar cistern and cerebellar cortical grooves. Theeft peridural CSF collection at D11 persists.
Discussion Intracranial pressure (ICP) results from the contribution of three intracranial fluid compartments: brain tissue (more than 80% fluid), intra-arterial blood and cerebrospinal fluid. If the volume of one compartment increases or decreases, the volume of one or both other com104
partments must decrease or increase for the total volume. Therefore, ICP remains the same: the so-called “Monro-Kellie model”. With low CSF pressure, an intradural venous dilation takes place, on the grounds of the theory that CSF swings, in an uninjured skull, complementary to achieved haematic volume 1214 . Other intracranial patterns include subdural
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collections (changing hydrostatic pressure) 21, displacement of encephalic structures (well depicted in sagittal and coronal sequences) 9, ventricular, basal cisterns, sylvian fissures volume reduction, often pituitary swelling 2,25. Spinal manifestations have seldom been reported 1,7,8. MRI study of the spine is irreplaceable when positive, to exclude tumours or expandeding process responsible for the patient’s condition. Spinal fluid collections are T1, T2 iso-intense to CSF, rarely, in SE PD, they are slightly hyperintense, because they lack the free CSF signal and also because they present a proteinous content 9. According to the Monro Kellie theory, pachymeningeal enhancement, venous plexus engorgement, subdural effusions and pituitary gland swelling represent alternative choices for intracranial volume balance, in the light of a CSF loss. Meningeal enhancement is thin and linear, implicates the pachymeninx without the leptomeninx and cortical grooves, because the dura mater has no joints responsible for the blood-brain barrier. So pressure gradient and volumetric increase in dural vessels cause a large off-side of fluid and enhancement in the dural interstice. Also subdural collections are bilateral, thin and without mass-effect. The absence of inflammatory cells suggests and sustains venous turgidity and intradural fluid effluvium, as the primum movens for a meningeal reaction, that is meningism, and not meningitis. Spinal MRI clarifies an equal, often correlative, perimedullar meningeal enhancement, and the dilation of anterior vertebral epidural venous plexus. Today another diagnostic technique, "Superior ophthalmic vein transorbital color doppler" is succesfully used in SIH. This vein is tributary to the cavernous sinus and also dilates by mutual consent to intracranial venous sinus engorgement. The venous sinus is enlarged and always open, never subject to intravascular thrombosis 15. The pituitary gland is highly vascularized and adjoins the cavernous sinus: its volumetric increase in SIH probably reflects a compensatory venous hyperemia, and rarely determines galactorrhea or hypopituitarism 2,15. Two principal theories account for the pathogenesis of orthostatic headache in SIH. The first claims sudden displacement of encephalic structures, because of low CSF content, with possible traction of the nervous-vascular complex. The second theory claims dilation of in-
The Neuroradiology Journal 21: 101-106, 2008
tracranial, pain sensitive venous structures as the origin of orthostatic headache. Subdural encephalic hygromas depend on hydrostatic pressure changes, in relation to CSF volumetric decrease. They can also appear in the spinal compartment. So hygromas are a second very common index of SIH. Their spinal origin is uncertain: they are probably caused by extra-arachnoid fluid discharge due to meningeal hyperemia 8. Hygromas are never found at C1-C2, where there is the highest dilation of the epidural venous plexus, and consequently trans-parietal discharge is impossible. Instead, in hygromas secondary to sinus thrombosis, pathogenesis is just the pachymeningeal thickness that creates an obstacle to CSF reabsorption through Pacchioni’s granulations 10. In the spinal compartment, the internal anterior epidural venous plexus is the commonest pattern: although continuous for all channels, its dilation reaches significantly high levels at C1-C2 25. Instead, a fluid retrospinal circumscripted collection, iso-intense to CSF in SE T1 and SE T2, and well depicted in SPIR T2, is typical. The anatomic characteristics render the C1-C2 metamere fit for the collection at issue. This space is the meeting-point of two triangles: the upper and the lower sub-occipital, and they contain very rich venous plexuses: the suboccipital venous plexus, the vertebral artery plexus, the external posterior vertebral plexus, and the deep cervical vein. These structures are related to the jugular bulb and dural sinus from mastoid veins and emissaries of condyles, and myriad anastomoses exist between the suboccipital and posterior external plexus. Furthermore, the suboccipital cavernous sinus has a pressure-regulator glomerule. So, the leakage theory appears least probable in the C1-C2 retrospinal space 25 (figure 1). When spinal findings are present, MRI will help to establish the site of any pachymeningeal leakage, showing the extradural collection. The anterior cervicalthoracic joint and thoracic inferior spinal tract are the commonest areas of hidden leakage and CSF loss. Finding the exact point of leakage can be very difficult, so often we use CT myelography or radionuclide cisternography. Fat suppression T2 myelocysternography MRI 11 used by us permitted the bloodless demonstration of the leakage-point. If SIH does not respond to medical treatments, an epidural blood patch is requested, using basculation of blood and contrast enhancement from the lumbar region to the cervical-thoracic joint 3,15. Lastly, the differential diagnosis of extramedullary collection 105
Morphological MRI and 3D Myelocisternography MRI in Spontaneous Intracranial Hypotension
includes: epidural haematomas, abscess, meningeal and neuro-enteric cysts. SIH epidural collections differ from epidural haematomas in their iso-intensity to CSF in SE T1. Only in a few cases described in literature 5,9,22 has the presence of a soft subarachnoid hemorrage led to the use of cerebral angiography to exclude a suspicion of ruptured aneurysm. Angiography disclosed diffuse marked enlargement of cortical and medullary veins (in accordance with the Monro-Kellie model), associated with enlargement of the anterior falx artery and with an attenuated meningeal blush 5. Epidural abscess usually presents wall enhancement and the clinical features are different. Meningeal cysts generally are posterior and not lateral like SIH collections. Neuro-enteric cysts are intradural and often related to vertebral anomalies 6.
F.A. Lupo
Conclusions Spontaneous intracranial hypotension is a clinical syndrome characterized by postural headache and linked with iconographic reports of meningism. MRI plays a fundamental role in documenting any cranio-spinal lesions. The neuroradiologist must recognize the clinical sindrome and show not only meningeal phenomena - encephalic hygromas, pituitary increase, spinal venous turgidity, cerebellar tonsil descent - but must also look for any small peridural CSF collections and related leakage, using fat suppression sequences. Old invasive techniques like CT myelography and or radionuclide cisternography should be avoided even if the depiction of meningeal leakage is often very complex and rare.
References 1 Albayram S, Wasserman BA, Yoseum DM et Al: Intracranial hypotension as a cause of radiculopathy from cervical epidural venous engorgement: case report. Am J Neuroradiol 23: 618-621, 2002. 2 Alvarez-Linera J, Escribano J, Benito Leon J et Al: Pituitary enlargement in patients with intracranial hypotension syndrome. Neurology 55: 1895-1897, 2000. 3 Bachmann-Mennega B, Philipps J, Haukamp F et Al: Spontaneous intracranial hypotension. A rare syndrome with good treatment options. Anaesthesist 53: 45-52, 2004. 4 Basak S, Klufas R, Hsu L: MRI of the Cervical Spine: Unusual Non-Neoplastic Disease. Appl Radiol 32: 3443, 2003. 5 Christoforidis GA, Mehta BA et Al: Spontaneous intracranial hypotension: report of four cases and review of the literature. Neuroradiology 40: 636-643, 1998. 6 Clarot F, Callonnec F, Douvrin F et Al: Giant cervical epidural veins after lumbar puncture in a case of intracranial hypotension. Am J Neuroradiol 21: 787-789, 2000. 7 Dillon WP: Spinal manifestations of intracranial hypotension [editorial]. Am J Neuroradiol 22: 1233-1234, 2001. 8 Fishman R, Dillon D: Dural enhancement and cerebral displacement secondary to intracranial hypotension. Neurology 43: 609-611, 1993. 9 Koss S.A, Ulmer JL, Hacein-Bey L: Angiographic features of spontaneous intracranial hypotension. Am J Neuroradiol 24: 704-706, 2003. 10 Inenaga C, Tanaka T, Sakai N et Al: Diagnostic and surgical strategies for intractable spontaneous intracranial hypotension. Neurosurg 94: 642-645, 2001. 11 Lupo FA, Perfetto SC et Al: Comparative study of CT cisternography, high resolution CT and MR cisternography in rhinorrea. Rivista di Neuroradiologia 13: 703710, 2000. 12 Mokri B: Historical Neurology. The Monro–Kellie hypothesis. Applications in CSF volume depletion. Neurology 56: 1746-1748, 2001. 13 Monro A: Observations on the structure and function of the nervous system. Edinburgh, Creech & J Johnson 1823: 5. 14 Paldino M, Mogilner AY, Tenner MS: Intracranial hypotension syndrome: a comprehensive review. Neurosurg Focus 15: 2, 2003.
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15 Rabin B.M, Roychowdhury S, Meyer JR et Al: Spontaneous Intracranial Hypotension: Spinal MR Findings. Am J Neuroradiol 19: 1034-1039, 1998. 16 Rai A, Rosen C, Carpenter J et Al: Epidural blood patch at C2: diagnosis and treatment of spontaneous intracranial hypotension. Am J Neuroradiol 26: 26632666, 2005. 17 Rando T, Fishman R: Spontaneous intracranial hypotension: report of two cases and review of the literature. Neurology 42: 481-487, 1992. 18 Renowden S, Gregory R, Hyman N et Al: Spontaneous intracranial hypotension. J Neurol Neurosug Psychiatry 59: 511-515, 1995. 19 Schaltenbrandt G: Neuere anshaungen zur pathophysiologic der liquorzirkulation. Zentralbl Neurochir 3: 290-300, 1938. 20 Schievink WI: Spontaneous Spinal Cerebrospinal Fluid Leaks and Intracranial Hypotension. JAMA 295: 22862296, 2006. 21 Schievink WI et Al: Pseudo-subarachnoid hemorrage: a CT–finding in spontaneous intracranial hypotension. Neurology 65: 135-137, 2005. 22 Schievink WI, Wijdicks EF, Meyer FB et Al: Spontaneous intracranial hypotension mimicking aneurysmal subarachnoid hemorrage. Neurosurgery 48: 513-517, 2001. 23 Wouter I, Schievink MD: Misdiagnosis of Spontaneous Intracranial Hypotension. Arch Neurol 60: 1713-1718, 2003. 24 Wouter I, Schievink M, Maya M et Al: Cranial MRI predicts outcome of spontaneous intracranial hypotension. Neurology 64: 1282-1284, 2005. 25 Yousry I, Forderreuther S, Moriggl B et Al: Cervical MR imaging in postural headache: MR signs and pathophysiologic implications. Am J Neuroradiol 22: 1239-1250, 2001. Fernando Antonio Lupo, MD U.O. Neuroradiologia AUSL LE/1 Ospedale Vito Fazzi Piazza F. Muratore 73100 Lecce, Italy Tel.: +39 0832332102 Fax: +39 0832661217 E-mail: [email protected]
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Morphological MRI and 3D Myelocisternography MRI in Spontaneous Intracranial Hypotension A Report of Four Cases F.A. LUPO, A. PALADINI, G. STICCHI, P. LUPO Neuroradiology Unit, Lecce Health Trust, “V. Fazzi” Hospital; Lecce, Italy
Key words: intracranial hypotension, postural headache, spontaneous subdural collection, pituitary swelling
SUMMARY – Spontaneous intracranial hypotension (SIH) is a polyhedric syndrome whose common denominator is postural headache. We describe four cases of spontaneous intracranial hypotension, their clinical-iconographic aspects, and emphasize the use of morphological MRI in the diagnosis and follow-up of this condition. In addition, we propose 3D myelocisternography MRI as a further contribution in cerebrospinal fluid losses causing postural headache.
Introduction Spontaneous intracranial hypotension (SIH), first described by Schaltenbrandt in 1938 19, is a syndrome characterized by a spontaneous reduction of cerebrospinal fluid pressure in the absence of trauma, surgery or lumbar puncture, and can follow minor trauma, like sneezing, coughing, etc. SIH usually results from CSF loss from leakages of meningeal sheath in points of minor resistance, with consequent CSF volume and pressure reduction. The hallmark symptom of SIH is postural headache, characterized by its appearance less than 15 minutes after standing, and by its disappearance or attenuation less than 30 minutes after lying down 18. Neck stiffness, nausea, vomiting, horizontal diplopia, dizziness, photophobia, deafness, and psychomotor excitement are often associated. CSF examination can be normal or slightly impaired by elevated proteins, or lymphocytic pleiocytosis, the presence of red cells or xanthochromia. CSF pressure is low (less than 60 mm H2O) and it can be impossible to measure with lumbar punture: the so-called “ dry tap” 6. The pharmacologic management of SIH is
similar to that of headache secondary to lumbar punture and includes: bed rest, analgesics, sedatives, caffeine, hydration, blood haemostasis or epidural saline infusion 15. Intracranial and spinal cord imaging includes morphological MRI, myelography MRI and radionuclide cisternography. These techniques are suitable not only for diagnosing this syndrome, but also for excluding any organic causes responsible for impaired CSF pressure. We describe four cases of postural headache, and show correlative brain and spinal cord changes with a low field strength MRI, using morphological studies and 3D myelocisternography MRI. Material and Methods We describe four patients aged 35-60 years, average age 45 years, two men and two women, with spontaneous intracranial hypotension who underwent MRI of brain using a low-field strength Philips Gyroscan T5 Intera 0.5 T. Brain study was done in the axial plane with SE T1, DP, T2, FLAIR sequences, and then using 0.2 M i.v. paramagnetic contrast me101
Morphological MRI and 3D Myelocisternography MRI in Spontaneous Intracranial Hypotension
F.A. Lupo
➜
Figure 1 Cervical MRI SPIR T1 mdc sequence at C1-C2; (TR 62 TE 14 Flip 30): normal anatomy of cervical venous structures. 1 axis body; 2 obliquus capitis inferior muscle; 3 medulla; 4 rectus capitis major muscle; 5 parotid gland. AIVVP Anterior internal vertebral venous plexus, PIEVVP posterior internal (arrow) and external (outlined arrow) vertebral venous plexus, DCV deep cervical vein. Figure 2 Diffuse meningeal thickening.
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A
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Figure 3 1 Pseudo-hyperplasia of pituitary gland; 2 cerebellar pseudotumor characterized by: cortical grooves smoothing, brain axis posterior surface impressio; prepontobulbar cistern volumetric reduction, initial descent of cerebellar tonsil into foramen magnu; 3 thickening of pachymeninx and internal anterior vertebral venous plexus.
dium [Gadobenate dimeglumine (Multihance - Bracco)]. Subsequently the spine was studied with SE T1 and TSE T2 axial and sagittal sequences and with sagittal fat-suppression SPIR TSE 102
T2 3D sequence, followed by axial and coronal MIP reconstructions. All patients were monitored with MRI for one to two months after onset. They also underwent lumbar punture and CSF examination.
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Case Reports Case 1: A 60-year-old man had severe orthostatic headache exacerbated by sudden standing and mitigated by bed-rest. He also had concomitant dizziness. He had no history of recent brain or spine trauma or lumbar punture. The patient did not have either fever or inflammatory index. Brain CT was negative. Brain MRI showed a diffuse thickening and a marked enhancement of the meningeal small sheath, from upper skull to vertex (figure 2), and pituitary swelling. There were no subdural flaps, or cerebellar tonsil engagement in the foramen magnum. Cervical spine MRI was negative for extradural collections, but demonstrated perimedullary dural enhancement. Lumbar punture identified a 40 mm H2O CSF pressure, without cytological abnormalities. The patient had no systemic pain, collagen disorder or vascular deficit. He gradually recovered thanks to bed-rest, anti-inflammatory drugs and bland steroids. Four months later, brain-spine MRI demonstrated a complete regression of the initial picture. Case 2: A 35-year-old man went to the emergency unit for severe headache and sudden muscle weakness. History-taking disclosed only two hours of exposure to the sun in early morning. He recalled a remote gastroresection for Crohn’s disease, now clinically and biochemically silent, so he was not receiving therapy. He had no fever, normal blood test, VES negative. Standing exacerbated his headache with horizontal diplopia. Brain and spine MRI revealed a pathological enhancement of the dura mater, and a soft fluid bilateral subdural flap to the convexity. No leakage was disclosed by myelocisternography MRI and lumbar puncture was negative. The patient improved with bed-rest, analgesics and rehydration. Six months later brain and spine MRI were normal. Case 3: A 36-year-old woman presented severe mainly occipital headache, rigor nucalis and psychomotor excitement. She was hospitalized in the infectious disease division. Symptoms had begun suddenly two days before hospitalization and were exacerbated by standing. Bed-rest attenuated but did not resolve the persistent NSAID-resistant headache. Blood tests and lumbar punture failed to disclose inflammation. CSF was mildly positive, and cytological examination showed reduced
The Neuroradiology Journal 21: 101-106, 2008
proteins. The persistence of severe headache led to administration of cortisone. Brain and total spine MRI showed a reactive diffuse encephalic and perimedullary dural thickening, cerebellar pseudotumor, characterized by cortical mantle thinning, brain axis posterior surface impression, prepontobulbar cistern volumetric reduction and initial descent of cerebellar tonsils into the foramen magnum (figure 3). Examination was completed with myelocisternography MRI, that revealed a small CSF collection in the dural sac at D11 and subsequently in the left nerve root (figure 4). History-taking failed to disclose trauma, so we confirmed the CSF drip was correlated to meningeal leakage, the stereotype of SIH 25. The patient did not respond to analgaesics, and reacted minimally to cortisone and bedrest. So doctors opted for haematic tamponade 16 . The patient initially refused the invasive therapy, but persistence of symptoms forced her to accept a blood patch. She recovered very quickly! (figure 5). Case 4: A 50-year-old woman with severe occipital headache, irresistible in orthostatism. History-taking failed to disclose trauma. The headache failed to respond to common anaegaesics and it was attenuated only with bedrest and cortisone. Brain MRI before and after i.v. contrast medium administration showed diffuse pachymeningeal thickening and pituitary swelling. MRI after four months displays normal findings: in particular there was no further meningeal irritation, and re-establishment of pituitary volume. The current clinical picture is normal and the headache has disappeared. Results We did not use alternative scans to standard brain and spine MRI sequences for SIH before and after i.v. contrast administration. However, SPIR T2 3D myelocisternography MRI with fat suppression was necessary to assess contingent meningeal leakeage. SE T1 sequences after i.v. contrast administration showed diffuse intense enhancement of the pachymeninx, and often a levelling of up– under tentorial grooves. In one of our four patients we were able to support the so-called “leakage”, with transfer of CSF into an extradural space, and dilation of the anterior peridural spinal venous plexus 6 . In all cases the pituitary gland was diffusely swollen and normal after therapy 15. 103
Morphological MRI and 3D Myelocisternography MRI in Spontaneous Intracranial Hypotension
F.A. Lupo
Figure 4 Myelography MRI: perimedullary subarachnoidal space at D11 (arrowhead); right and left radicular pouch at D11 ( small arrows); left peridural CSF collection and fistulous pathway (large arrow).
A
B
C
Figure 5 A) SE Ax T1 mdc. B) Sagittal SE T1 mdc. C) Myelography. Examinations after therapy and clinical picture resolution. Note: dural thickening, cervical venous turgor and pituitary gland pseudo- hyperplasia disappearance; reduction of cerebellar impression on brain axis and re-expansion of prepontobulbar cistern and cerebellar cortical grooves. Theeft peridural CSF collection at D11 persists.
Discussion Intracranial pressure (ICP) results from the contribution of three intracranial fluid compartments: brain tissue (more than 80% fluid), intra-arterial blood and cerebrospinal fluid. If the volume of one compartment increases or decreases, the volume of one or both other com104
partments must decrease or increase for the total volume. Therefore, ICP remains the same: the so-called “Monro-Kellie model”. With low CSF pressure, an intradural venous dilation takes place, on the grounds of the theory that CSF swings, in an uninjured skull, complementary to achieved haematic volume 1214 . Other intracranial patterns include subdural
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collections (changing hydrostatic pressure) 21, displacement of encephalic structures (well depicted in sagittal and coronal sequences) 9, ventricular, basal cisterns, sylvian fissures volume reduction, often pituitary swelling 2,25. Spinal manifestations have seldom been reported 1,7,8. MRI study of the spine is irreplaceable when positive, to exclude tumours or expandeding process responsible for the patient’s condition. Spinal fluid collections are T1, T2 iso-intense to CSF, rarely, in SE PD, they are slightly hyperintense, because they lack the free CSF signal and also because they present a proteinous content 9. According to the Monro Kellie theory, pachymeningeal enhancement, venous plexus engorgement, subdural effusions and pituitary gland swelling represent alternative choices for intracranial volume balance, in the light of a CSF loss. Meningeal enhancement is thin and linear, implicates the pachymeninx without the leptomeninx and cortical grooves, because the dura mater has no joints responsible for the blood-brain barrier. So pressure gradient and volumetric increase in dural vessels cause a large off-side of fluid and enhancement in the dural interstice. Also subdural collections are bilateral, thin and without mass-effect. The absence of inflammatory cells suggests and sustains venous turgidity and intradural fluid effluvium, as the primum movens for a meningeal reaction, that is meningism, and not meningitis. Spinal MRI clarifies an equal, often correlative, perimedullar meningeal enhancement, and the dilation of anterior vertebral epidural venous plexus. Today another diagnostic technique, "Superior ophthalmic vein transorbital color doppler" is succesfully used in SIH. This vein is tributary to the cavernous sinus and also dilates by mutual consent to intracranial venous sinus engorgement. The venous sinus is enlarged and always open, never subject to intravascular thrombosis 15. The pituitary gland is highly vascularized and adjoins the cavernous sinus: its volumetric increase in SIH probably reflects a compensatory venous hyperemia, and rarely determines galactorrhea or hypopituitarism 2,15. Two principal theories account for the pathogenesis of orthostatic headache in SIH. The first claims sudden displacement of encephalic structures, because of low CSF content, with possible traction of the nervous-vascular complex. The second theory claims dilation of in-
The Neuroradiology Journal 21: 101-106, 2008
tracranial, pain sensitive venous structures as the origin of orthostatic headache. Subdural encephalic hygromas depend on hydrostatic pressure changes, in relation to CSF volumetric decrease. They can also appear in the spinal compartment. So hygromas are a second very common index of SIH. Their spinal origin is uncertain: they are probably caused by extra-arachnoid fluid discharge due to meningeal hyperemia 8. Hygromas are never found at C1-C2, where there is the highest dilation of the epidural venous plexus, and consequently trans-parietal discharge is impossible. Instead, in hygromas secondary to sinus thrombosis, pathogenesis is just the pachymeningeal thickness that creates an obstacle to CSF reabsorption through Pacchioni’s granulations 10. In the spinal compartment, the internal anterior epidural venous plexus is the commonest pattern: although continuous for all channels, its dilation reaches significantly high levels at C1-C2 25. Instead, a fluid retrospinal circumscripted collection, iso-intense to CSF in SE T1 and SE T2, and well depicted in SPIR T2, is typical. The anatomic characteristics render the C1-C2 metamere fit for the collection at issue. This space is the meeting-point of two triangles: the upper and the lower sub-occipital, and they contain very rich venous plexuses: the suboccipital venous plexus, the vertebral artery plexus, the external posterior vertebral plexus, and the deep cervical vein. These structures are related to the jugular bulb and dural sinus from mastoid veins and emissaries of condyles, and myriad anastomoses exist between the suboccipital and posterior external plexus. Furthermore, the suboccipital cavernous sinus has a pressure-regulator glomerule. So, the leakage theory appears least probable in the C1-C2 retrospinal space 25 (figure 1). When spinal findings are present, MRI will help to establish the site of any pachymeningeal leakage, showing the extradural collection. The anterior cervicalthoracic joint and thoracic inferior spinal tract are the commonest areas of hidden leakage and CSF loss. Finding the exact point of leakage can be very difficult, so often we use CT myelography or radionuclide cisternography. Fat suppression T2 myelocysternography MRI 11 used by us permitted the bloodless demonstration of the leakage-point. If SIH does not respond to medical treatments, an epidural blood patch is requested, using basculation of blood and contrast enhancement from the lumbar region to the cervical-thoracic joint 3,15. Lastly, the differential diagnosis of extramedullary collection 105
Morphological MRI and 3D Myelocisternography MRI in Spontaneous Intracranial Hypotension
includes: epidural haematomas, abscess, meningeal and neuro-enteric cysts. SIH epidural collections differ from epidural haematomas in their iso-intensity to CSF in SE T1. Only in a few cases described in literature 5,9,22 has the presence of a soft subarachnoid hemorrage led to the use of cerebral angiography to exclude a suspicion of ruptured aneurysm. Angiography disclosed diffuse marked enlargement of cortical and medullary veins (in accordance with the Monro-Kellie model), associated with enlargement of the anterior falx artery and with an attenuated meningeal blush 5. Epidural abscess usually presents wall enhancement and the clinical features are different. Meningeal cysts generally are posterior and not lateral like SIH collections. Neuro-enteric cysts are intradural and often related to vertebral anomalies 6.
F.A. Lupo
Conclusions Spontaneous intracranial hypotension is a clinical syndrome characterized by postural headache and linked with iconographic reports of meningism. MRI plays a fundamental role in documenting any cranio-spinal lesions. The neuroradiologist must recognize the clinical sindrome and show not only meningeal phenomena - encephalic hygromas, pituitary increase, spinal venous turgidity, cerebellar tonsil descent - but must also look for any small peridural CSF collections and related leakage, using fat suppression sequences. Old invasive techniques like CT myelography and or radionuclide cisternography should be avoided even if the depiction of meningeal leakage is often very complex and rare.
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