Clinical Radiology(1992) 45, 134 136
Case Report: CT and MRI of the Cauda Equina Syndrome in Ankylosing Spondylitis R. W. K E R S L A K E , L. A. M I T C H E L L a n d B. S. W O R T H I N G T O N
Sub-Department of Academic Radiology, University Hospital, Nottingham The clinical and radiological findings in a patient with long-standing ankylosing spondylitis who developed the clinical features of a cauda equina syndrome are presented. CT and MRI revealed characteristic expansion of the lumbar spinal canal with scalloping of the laminae and spinous processes related to the presence of dorsal dural diverticulae. M R I permitted confident exclusion of other intradural pathology without recourse to invasive investigations. Kerslake, R.W., Mitchell, L.A. & W o r t h i n g t o n , B.S. (1992). Clinical Radiology 45, 134 136. Case Report: C T a n d M R I of the C a u d a E q u i n a S y n d r o m e in A n k y l o s i n g Spondylitis
A n k y l o s i n g spondylitis is a chronic disease primarily affecting the spine. Neurological m a n i f e s t a t i o n s are relatively u n u s u a l and principally relate to spinal cord compression due to atlantoaxial s u b l u x a t i o n or direct spinal cord injury following t r a u m a to the ankylosed spine. Isolated thoracic a n d l u m b o s a c r a l nerve root lesions may occur. A n u n c o m m o n a n d incompletely u n d e r s t o o d complication is the d e v e l o p m e n t of a gradually progressive c a u d a e q u i n a s y n d r o m e (CES). Less t h a n 60 cases have been reported in the world literature to date, though the c o n d i t i o n m a y well be more c o m m o n than has generally been recognized. M R I has only been used in a few of the most recent cases ( R u b e n s t e i n et al., 1989; Abello et al., 1988) a n d we report a further case in which M R I proved to be of value in confirming the diagnosis and in excluding other pathologies.
CASE REPORT A 63-year-old female presented with a 2 year history of bilateral lower limb numbnessand pain whichwas worst on the left. There was no disturbance of bowel or bladder function. She had been diagnosed as having ankylosing spondylitis (AS) at the age of 18 years. Neurological examination revealed sensory impairment in the left L5 to $4 and the right SI dermatomes. The tendon reflexes were absent at both ankles and at the left knee; anal tone was preserved. There was no motor deficit or muscle wasting. Conventional radiographs showed extensiveankylosis in the lumbar region. CT revealed a wide spinal canal with scalloping of the pedicles, laminae and spinous processes at multiple levels(Fig. 1). A limited MR study (due to patient claustrophobia) was performed at 0.15 T. This demonstrated a wide lumbar thecal sac with extensivedural diverticulae extending betweenthe posterior neural arches and causing scallopingof the laminae and spinous processes (Fig. 2). The contents of the dural diverticulae were isointense with cerebrospinal fluid (CSF) on the T1weighted sequences obtained. There was no evidence of nerve root compressionby either bony encroachment on the exit canals or the dural diverticulae,whichwere situated posterior to the exit foraminae (Fig. 2). No intradural mass lesion was identified.
DISCUSSION The c a u d a e q u i n a s y n d r o m e is a constellation o f s y m p t o m s a n d signs that usually result from a compressive lesion located in the u p p e r l u m b a r region. Typically, Correspondenceto: Dr R.W. Kerstake, 32 Elm Road, Windsor, Berks SL4 3ND.
Fig. 1 Axial CT scan at the L2/3 leveldemonstrating scallopingof the pedictes, laminae and spinous process. multiple l u m b a r roots are involved bilaterally a n d presenting features include back a n d extremity pain, impotence, decreased sphincter tone, overflow incontinence, muscle weakness a n d wasting a n d c u t a n e o u s sensory loss affecting the l u m b o s a c r a l dermatomes. These features are often progressive. Potential causes include i n t r a m e d u l l ary or extramedullary tumours, intervertebral disc herniation, or, less c o m m o n l y , osseous changes due to Paget's disease, osteomyelitis or osteoarthrosis of the facet joints (Mitchell et al., 1990). The c a u d a e q u i n a s y n d r o m e of AS has a n insidious onset a n d usually becomes a p p a r e n t some 16 35 years after AS is first diagnosed, when active i n f l a m m a t o r y disease is no longer present (Bowie a n d G l a s g o w 1961; Bartleson et al., 1983). Sensory s y m p t o m s a n d distur-
CT AND MRI OF THE CES IN ANKYLOSING SPONDYLITIS
(a)
(b) Fig. 2 M R images obtained at 0.15 T (SE 500/40 sequence). Sagittal (a) and axial (b) at the LI/2 level. Extensive ankylosis is present in the lumbar region. The wide dural sac and dorsal dural diverticulae are well shown. The position of the spinal cord and conus is normal. Axial images (b) demonstrate the diverticulae to be asymmetrically located posterior to the exit foraminae (arrows). An intradural mass lesion is excluded, even on this limited study.
bance of bladder function are common though m o t o r deficits are less prominent. Pain may be a feature (Bartleson et al., 1983). Etectromyography shows abnormalities consistent with multiple lumbosacral radiculopathies (Young et al., 1981). The condition is usually slowly progressive and neither medical nor surgical therapy has proved to be of value; indeed, surgery may be followed by clinical deterioration (Bartleson et al., 1983). The CES of AS is often diagnosed at a relatively late stage and compressive lesions of the upper lumbar region have to be excluded. If myelography is performed, a widened
135
thecal sac and variably sized dorsal diverticulae which m a y fill with contrast are demonstrated. However, myelography cannot be recommended as it may be technically difficult in patients with an ankylosed spine and m a y exacerbate the neurological condition (Bartleson et al., 1983; Young et al., 1981). Some authors suggest that the CT demonstration of dorsal arachnoid diverticulae and erosions of the posterior arches in the context of a patient with long-standing AS and a slowly progressive CES are sufficiently specific for the need for myelography to be eliminated (Bartleson et al., 1983; Young et al., 1981; Mitchell et al., 1990). However, CT may not be capable of excluding intradural mass lesions in the absence of intrathecal contrast. Like CT, M R I in this condition demonstrates enlargement of the lumbar canal with irregular scalloping of the posterior elements. More importantly, the presence of dural diverticulae with contents which are isointense with CSF can be confirmed and other intradural pathologies can be excluded in a totally non-invasive manner. In a few cases, M R I shows displacement of the spinal cord. This is considered by some authors to be due to the presence of arachnoid cysts and to be responsible for the neurological dysfunction (Abello et al., 1988). More usually, there is no evidence of compression of the spinal cord or nerve roots by either bone or dural diverticulae. Foraminal narrowing is rarely seen and the dural diverticulae are located posterior to the intervertebral foraminae (Bartleson et al., 1983; Matthews, 1968). A number of possible mechanisms have been proposed to explain the CES. These include demyelination, ischaemia or compression and subsequent atrophy related to previous arachnoiditis. Post-irradiation myelopathy is excluded as a cause as only a minority of patients with the CES of AS have received previous irradiation. There are few reports in which pathological material has been obtained and only a single post-mortem study has been reported (Matthews, 1968). The dorsal root ganglia and nerve roots are sensitive to ischaemia and this could result from the small vessel angiitis which is known to occur in AS. Whilst such a mechanism is attractive in explaining the documented nerve root atrophy and demyelination it does not account for the presence of the dural diverticulae. It has been proposed that both the dural diverticulae and the neurological syndrome may be caused by arachnoiditis occurring in the relatively early stages of the disease (Matthews, 1968). Evidence of arachnoiditis has been found in those patients operated on within a few years of the onset of neurological symptoms (Hague, 1961) but not when surgery has been performed in the later stages of the disease. The dural diverticulae could be caused by arachnoiditis leading to the formation of small blind pouches which subsequently become enlarged by the force of arterial pulsations transmitted through the CSF and produce the characteristic bone erosions (Matthews, 1968). The relationship of the dural diverticulae to nerve root dysfunction however remains controversial. Although some degenerative changes are found in the roots of the cauda equina and demyelination has been observed within the medial posterior columns of the spinal cord this is thought to be secondary to degeneration in the posterior roots rather than evidence of primary spinal cord disease (Matthews, 1968). The CES is an infrequently recognized and poorly understood complication of AS. Diagnosis is based on the
136
CLINICALRADIOLOGY
typical clinical features of a slowly progressive CES and the demonstration of dorsal dural diverticulae and scalloping of the posterior vertebral elements at one or more lumbar levels. M R I is of particular value in being capable of excluding intraspinal masses in a totally non-invasive manner and may assist in establishing the diagnosis at an earlier stage. Acknowledgements. We are indebted to Dr R. A. Haddow for performing the CT study. We thank Dr B. P. Hunt and T. Hope for agreeing to publication of this case. Dr R. W. Kerslake is supported by the Department of Health and the Medical Research Council. REFERENCES Abello, R, Rovira, M, Sanz, MP, Gili, J, Capdevila, A, Escalada, Jet al. (1989). MRI and CT of ankylosing spondylitis with vertebral scalloping. Neuroradiology, 30, 272 275. Bartleson, JD, Cohen, MD, Harrington, TM, Goldstein, NP &
Ginsb_urg, WW (1983). Cauda equina syndrome secondary to longstanding ankylosing spondylitis. Annals of Neurology, 14, 662 666. Bowie, EA & Glasgow, GL (1961). Cauda equina lesions associated with ankylosing spondylitis. Report of three cases. British Medical Journal, 2, 24 27. Hauge, T (1961). Chronic rheumatoid polyarthritis and spondyloarthritis associated with neurological symptoms and signs occasionally simulating an intraspinal expansive process. Chirurgiea Scandinavica, 120, 395 401. Matthews, WB (1968). The neurological complications of ankylosing spondylitis. Journal of the Neurological Sciences, 6, 561-573. Mitchell, M J, Sartoris, DJ, Moody, D & Resnick, D (1990). Cauda equina syndrome complicating ankylosing spondylitis. Radiology, 175, 521-525. Rubenstein, D J, Alvarez, O, Ghelman, B & Marchisello, P (1989). Case report: Cauda equina syndrome complicating ankylosing spondylitis: MR features. Journal of Computer Assisted Tomography, 13, 511-513. Young, A, Dixon, A, Getty, J, Renton, P & Vacher, H (1981). Case report: caudia equina syndrome complicating ankylosing spondylitis: use of electromyography and computerised tomography in diagnosis. Annals of the Rheumatic Diseases, 40, 317 322.
Case Report: CT and MRI of the Cauda Equina Syndrome in Ankylosing Spondylitis R. W. K E R S L A K E , L. A. M I T C H E L L a n d B. S. W O R T H I N G T O N
Sub-Department of Academic Radiology, University Hospital, Nottingham The clinical and radiological findings in a patient with long-standing ankylosing spondylitis who developed the clinical features of a cauda equina syndrome are presented. CT and MRI revealed characteristic expansion of the lumbar spinal canal with scalloping of the laminae and spinous processes related to the presence of dorsal dural diverticulae. M R I permitted confident exclusion of other intradural pathology without recourse to invasive investigations. Kerslake, R.W., Mitchell, L.A. & W o r t h i n g t o n , B.S. (1992). Clinical Radiology 45, 134 136. Case Report: C T a n d M R I of the C a u d a E q u i n a S y n d r o m e in A n k y l o s i n g Spondylitis
A n k y l o s i n g spondylitis is a chronic disease primarily affecting the spine. Neurological m a n i f e s t a t i o n s are relatively u n u s u a l and principally relate to spinal cord compression due to atlantoaxial s u b l u x a t i o n or direct spinal cord injury following t r a u m a to the ankylosed spine. Isolated thoracic a n d l u m b o s a c r a l nerve root lesions may occur. A n u n c o m m o n a n d incompletely u n d e r s t o o d complication is the d e v e l o p m e n t of a gradually progressive c a u d a e q u i n a s y n d r o m e (CES). Less t h a n 60 cases have been reported in the world literature to date, though the c o n d i t i o n m a y well be more c o m m o n than has generally been recognized. M R I has only been used in a few of the most recent cases ( R u b e n s t e i n et al., 1989; Abello et al., 1988) a n d we report a further case in which M R I proved to be of value in confirming the diagnosis and in excluding other pathologies.
CASE REPORT A 63-year-old female presented with a 2 year history of bilateral lower limb numbnessand pain whichwas worst on the left. There was no disturbance of bowel or bladder function. She had been diagnosed as having ankylosing spondylitis (AS) at the age of 18 years. Neurological examination revealed sensory impairment in the left L5 to $4 and the right SI dermatomes. The tendon reflexes were absent at both ankles and at the left knee; anal tone was preserved. There was no motor deficit or muscle wasting. Conventional radiographs showed extensiveankylosis in the lumbar region. CT revealed a wide spinal canal with scalloping of the pedicles, laminae and spinous processes at multiple levels(Fig. 1). A limited MR study (due to patient claustrophobia) was performed at 0.15 T. This demonstrated a wide lumbar thecal sac with extensivedural diverticulae extending betweenthe posterior neural arches and causing scallopingof the laminae and spinous processes (Fig. 2). The contents of the dural diverticulae were isointense with cerebrospinal fluid (CSF) on the T1weighted sequences obtained. There was no evidence of nerve root compressionby either bony encroachment on the exit canals or the dural diverticulae,whichwere situated posterior to the exit foraminae (Fig. 2). No intradural mass lesion was identified.
DISCUSSION The c a u d a e q u i n a s y n d r o m e is a constellation o f s y m p t o m s a n d signs that usually result from a compressive lesion located in the u p p e r l u m b a r region. Typically, Correspondenceto: Dr R.W. Kerstake, 32 Elm Road, Windsor, Berks SL4 3ND.
Fig. 1 Axial CT scan at the L2/3 leveldemonstrating scallopingof the pedictes, laminae and spinous process. multiple l u m b a r roots are involved bilaterally a n d presenting features include back a n d extremity pain, impotence, decreased sphincter tone, overflow incontinence, muscle weakness a n d wasting a n d c u t a n e o u s sensory loss affecting the l u m b o s a c r a l dermatomes. These features are often progressive. Potential causes include i n t r a m e d u l l ary or extramedullary tumours, intervertebral disc herniation, or, less c o m m o n l y , osseous changes due to Paget's disease, osteomyelitis or osteoarthrosis of the facet joints (Mitchell et al., 1990). The c a u d a e q u i n a s y n d r o m e of AS has a n insidious onset a n d usually becomes a p p a r e n t some 16 35 years after AS is first diagnosed, when active i n f l a m m a t o r y disease is no longer present (Bowie a n d G l a s g o w 1961; Bartleson et al., 1983). Sensory s y m p t o m s a n d distur-
CT AND MRI OF THE CES IN ANKYLOSING SPONDYLITIS
(a)
(b) Fig. 2 M R images obtained at 0.15 T (SE 500/40 sequence). Sagittal (a) and axial (b) at the LI/2 level. Extensive ankylosis is present in the lumbar region. The wide dural sac and dorsal dural diverticulae are well shown. The position of the spinal cord and conus is normal. Axial images (b) demonstrate the diverticulae to be asymmetrically located posterior to the exit foraminae (arrows). An intradural mass lesion is excluded, even on this limited study.
bance of bladder function are common though m o t o r deficits are less prominent. Pain may be a feature (Bartleson et al., 1983). Etectromyography shows abnormalities consistent with multiple lumbosacral radiculopathies (Young et al., 1981). The condition is usually slowly progressive and neither medical nor surgical therapy has proved to be of value; indeed, surgery may be followed by clinical deterioration (Bartleson et al., 1983). The CES of AS is often diagnosed at a relatively late stage and compressive lesions of the upper lumbar region have to be excluded. If myelography is performed, a widened
135
thecal sac and variably sized dorsal diverticulae which m a y fill with contrast are demonstrated. However, myelography cannot be recommended as it may be technically difficult in patients with an ankylosed spine and m a y exacerbate the neurological condition (Bartleson et al., 1983; Young et al., 1981). Some authors suggest that the CT demonstration of dorsal arachnoid diverticulae and erosions of the posterior arches in the context of a patient with long-standing AS and a slowly progressive CES are sufficiently specific for the need for myelography to be eliminated (Bartleson et al., 1983; Young et al., 1981; Mitchell et al., 1990). However, CT may not be capable of excluding intradural mass lesions in the absence of intrathecal contrast. Like CT, M R I in this condition demonstrates enlargement of the lumbar canal with irregular scalloping of the posterior elements. More importantly, the presence of dural diverticulae with contents which are isointense with CSF can be confirmed and other intradural pathologies can be excluded in a totally non-invasive manner. In a few cases, M R I shows displacement of the spinal cord. This is considered by some authors to be due to the presence of arachnoid cysts and to be responsible for the neurological dysfunction (Abello et al., 1988). More usually, there is no evidence of compression of the spinal cord or nerve roots by either bone or dural diverticulae. Foraminal narrowing is rarely seen and the dural diverticulae are located posterior to the intervertebral foraminae (Bartleson et al., 1983; Matthews, 1968). A number of possible mechanisms have been proposed to explain the CES. These include demyelination, ischaemia or compression and subsequent atrophy related to previous arachnoiditis. Post-irradiation myelopathy is excluded as a cause as only a minority of patients with the CES of AS have received previous irradiation. There are few reports in which pathological material has been obtained and only a single post-mortem study has been reported (Matthews, 1968). The dorsal root ganglia and nerve roots are sensitive to ischaemia and this could result from the small vessel angiitis which is known to occur in AS. Whilst such a mechanism is attractive in explaining the documented nerve root atrophy and demyelination it does not account for the presence of the dural diverticulae. It has been proposed that both the dural diverticulae and the neurological syndrome may be caused by arachnoiditis occurring in the relatively early stages of the disease (Matthews, 1968). Evidence of arachnoiditis has been found in those patients operated on within a few years of the onset of neurological symptoms (Hague, 1961) but not when surgery has been performed in the later stages of the disease. The dural diverticulae could be caused by arachnoiditis leading to the formation of small blind pouches which subsequently become enlarged by the force of arterial pulsations transmitted through the CSF and produce the characteristic bone erosions (Matthews, 1968). The relationship of the dural diverticulae to nerve root dysfunction however remains controversial. Although some degenerative changes are found in the roots of the cauda equina and demyelination has been observed within the medial posterior columns of the spinal cord this is thought to be secondary to degeneration in the posterior roots rather than evidence of primary spinal cord disease (Matthews, 1968). The CES is an infrequently recognized and poorly understood complication of AS. Diagnosis is based on the
136
CLINICALRADIOLOGY
typical clinical features of a slowly progressive CES and the demonstration of dorsal dural diverticulae and scalloping of the posterior vertebral elements at one or more lumbar levels. M R I is of particular value in being capable of excluding intraspinal masses in a totally non-invasive manner and may assist in establishing the diagnosis at an earlier stage. Acknowledgements. We are indebted to Dr R. A. Haddow for performing the CT study. We thank Dr B. P. Hunt and T. Hope for agreeing to publication of this case. Dr R. W. Kerslake is supported by the Department of Health and the Medical Research Council. REFERENCES Abello, R, Rovira, M, Sanz, MP, Gili, J, Capdevila, A, Escalada, Jet al. (1989). MRI and CT of ankylosing spondylitis with vertebral scalloping. Neuroradiology, 30, 272 275. Bartleson, JD, Cohen, MD, Harrington, TM, Goldstein, NP &
Ginsb_urg, WW (1983). Cauda equina syndrome secondary to longstanding ankylosing spondylitis. Annals of Neurology, 14, 662 666. Bowie, EA & Glasgow, GL (1961). Cauda equina lesions associated with ankylosing spondylitis. Report of three cases. British Medical Journal, 2, 24 27. Hauge, T (1961). Chronic rheumatoid polyarthritis and spondyloarthritis associated with neurological symptoms and signs occasionally simulating an intraspinal expansive process. Chirurgiea Scandinavica, 120, 395 401. Matthews, WB (1968). The neurological complications of ankylosing spondylitis. Journal of the Neurological Sciences, 6, 561-573. Mitchell, M J, Sartoris, DJ, Moody, D & Resnick, D (1990). Cauda equina syndrome complicating ankylosing spondylitis. Radiology, 175, 521-525. Rubenstein, D J, Alvarez, O, Ghelman, B & Marchisello, P (1989). Case report: Cauda equina syndrome complicating ankylosing spondylitis: MR features. Journal of Computer Assisted Tomography, 13, 511-513. Young, A, Dixon, A, Getty, J, Renton, P & Vacher, H (1981). Case report: caudia equina syndrome complicating ankylosing spondylitis: use of electromyography and computerised tomography in diagnosis. Annals of the Rheumatic Diseases, 40, 317 322.
