Journal ofNeurology, Neurosuirgery, and Psychiatry, 1976, 39, 1172-1178

Cauda equina syndrome in ankylosing spondylitis:a report of six cases

I. HASSAN

From the Wessex Neurological Centre, Southampton University Hospitals, Southampton

SYNOPSIS Six patients with ankylosing spondylitis and features of a cauda equina syndrome are

described. The myelographic findings are discussed in relation to the pathogenesis of the disorder andits natural history. Present experience suggests that the cauda equina syndrome is a more common

complication of ankylosing spondylitis than is usually thought.

The nervous system may be involved in ankylosingspondylitis as a result of atlantoaxial subluxation orspinal fractures and by development ofa cauda equinasyndrome (Matthews, 1968). In addition, an increasedincidence of multiple sclerosis in patients with anky-losing spondylitis has been described recently(Thomas et al., 1974). Eighteen cases of ankylosingspondylitis complicated by a cauda equina syndromehave been reported (Bowie and Glasgow, 1961;Hauge, 1961; Lee and Waters, 1962; McGill, 1966;Matthews, 1968; Rosenkranz, 1971; Gordon andYudell, 1973; Russell et al., 1973; Thomas et al.,1974). These cases are reviewed in Table 1. While thisnumber suggests that the cauda equina syndrome is arare complication of ankylosing spondylitis, thepresent study indicates that this complication is morecommon than is usually thought.

CLINICAL MATERIAL

This investigation is based on a study of six patientswith ankylosing spondylitis who were referred to theWessex Neurological Centre between 1967 and 1975for investigation of their neurological complaints. Inall six the diagnosis of ankylosing spondylitis hadbeen established reliably on clinical and radiologicalgrounds. The average age was 54 years (range 49 to59 years) and the average duration of the spondylitiswas 29 years (range 25 to 37 years). Tests for rheuma-toid factor were negative in all the patients. Threepatients (cases 4, 5, and 6) had experienced severalattacks of iritis. There was radiological evidence of

Address for correspondence: 21 Weaverthorpe Road, WoodthorpeNottingham.(Accepted 18 August 1976.)

pulmonary fibrosis in three patients (cases 2, 4, and 5).Five of the six patients had received radiotherapy forthe ankylosing spondylitis (Table 2).

CASE 1

A 59 year old man was seen in 1967 because of pain inthe outer border of his left foot which had beenpresent for nine years. He had suffered from anky-losing spondylitis since 1940 and had received radio-therapy in 1946. Clinical examination revealedwasting and weakness of the left calf, the left anklejerk and plantar response were absent, and there wassensory loss in the fifth lumbar and upper four sacraldermatomes on the left side. Oil myelographyrevealed posteriorly situated lumbar cysts (Figs. 1 and2). No progression in his neurological signs hadoccurred during a follow-up period of four years.

CASE 2A 49 year old man was seen in 1968 because ofnumbness of the posterior surface of his left leg whichhad been present for nine years. He had suffered fromankylosing spondylitis for 30 years and had receivedradiotherapy in 1947. On clinical examination therewas wasting and weakness of both buttocks andcalves, both ankle jerks and plantar responses wereabsent, and there was sensory loss in the fifth lumbarand in all the sacral dermatomes. He developedsystemic arterial hypertension in 1973 but his neuro-logical signs have not progressed.

CASE 3A 49 year old man presented in 1968 with numbnessof his left foot which had been present for fourmonths. He had also noticed a poor urinary stream.

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TABLE 2DETAILS OF SIX CASES OF CAUDA EQUINA SYNDROME IN ANKYLOSING SPONDYLITIS REPORTED IN THIS SERIES

DurationCase Age, sex ofAS DXT Neurological complaint Neurological signs Myelogram

(yr) (yr)

1 59 M 27 Yes Pain in L foot for 9 yr Wasting and weakness of Lumbar cystsL calf. Absent L ankle jerk.Sensory loss L5-S5 (L)

2 49 M 30 Yes Numbness in back of L leg Wasting and weakness of Not donefor 9 yr. Incontinence of calves and buttocks, absenturine for 3 m ankle jerks, sensory loss L5-S5

(bilat.)3 49 M 25 No Numbness in L foot for 4 m Wasting and weakness of calves Lumbar cysts

and buttocks, absent anklejerks, sensory loss SI-S5(bilat.)

4 59 M 25 Yes Weakness ofR foot for 3 yr Wasting and weakness of Mid-thoracic cystsR calf, absent R ankle jerk,sensory loss S1-S2 (R)

5 54 M 28 Yes Incontinence of urine for 12 m Wasting and weakness of Lumbar cystscalves and buttocks, absentankle jerks, sensory loss S1-S5(bilat.)

6 55 F 37 Yes Pain and neuropathic ulcers Wasting and weakness of Not donein both legs for 20 yr. calves and buttocks, absentIncontinence of urine for 4 m ankle jerks, sensory loss SI-S5

L5 (bilat.)

He had suffered from ankylosing spondylitis for 25years; he had never been treated with radiotherapy.There was wasting and weakness of both buttocks andcalves, absent ankle jerks and plantar responses, anda sensory loss in all the sacral dermatomes. Oilmyelography revealed posteriorly situated lumbarcysts. No progression in the neurological signs hadoccurred in three years.

CASE 4

A 59 year old man was referred in 1974 with weaknessof plantar flexion of the right foot for three years.He had suffered from ankylosing spondylitis for 25years and had received radiotherapy in 1950. Physicalexamination revealed wasting and weakness of hisright calf, the right ankle jerk and plantar responsewere absent, and there was sensory loss in the firsttwo sacral dermatomes on the right side. Oil myelo-graphy revealed posteriorly situated cysts in the midthoracic region. No progression of the neurologicalsigns has been noted during a follow-up period ofone year.

CASE 5

A 54 year old man presented in 1975 with a historyof urinary incontinence for 12 months. He gave ahistory of ankylosing spondylitis for 28 years and hadbeen treated with radiotherapy to his cervical spine

and hips in 1958 and 1971. On examination there waswasting and weakness of both buttocks and calves,his ankle jerks and plantar responses were absent andthe sensory loss affected all the sacral dermatomes.A water soluble contrast radiculogram revealedmultiple large diverticula situated posterolaterallyand between the laminae in the lumbar region (Fig.3a and b).

CASE 6

A 55 year old woman with a 37 year history of anky-losing spondylitis was seen in 1975. Since 1953 shehad suffered from pain and neuropathic ulceration ofboth legs. She had been incontinent of urine for fourmonths. She had received radiotherapy in 1946.Physical examination revealed wasting and weaknessof both buttocks and calves, absent ankle jerks andplantar responses, and sensory loss in the fifth lumbarand all sacral dermatomes.

DISCUSSION

In the patients reported in this study the onset of thecauda equina syndrome occurred between 17 and 28years after the onset of the ankylosing spondylitis,during periods when the disease was relatively in-active as judged by symptoms and erythrocyte sedi-mentation rates. The varied nature of the initial

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FIG. 1 Case 1. Oil myelogram showing posteriorlysituated diverticula in the lumbar theca (patient supine).

neurological symptoms and their long durationaccount for the difficulty in early recognition of thecauda equina syndrome in patients with ankylosingspondylitis in whom pain in the buttocks and thighsmay be attributed to sacroiliac joint inflammation.

Urinary incontinence was the presenting complaintin case 5, in all three patients described by Bowie andGlasgow (1961), in cases 2 and 3 reported by Hauge(1961), in Rosenkrantz's (1971) case, in case 2 ofGordon and Yudell (1973), and in case 3 of Thomaset al. (1974). It subsequently became the most promi-nent symptom in the case described by Lee andWaters (1962), McGill (1966), and Matthews (1968)(case 4). Other presenting symptoms were pain,numbness or weakness in the lower limbs, impotence,and difficulties with micturition and defaecation.The significance of posteriorly situated diverticula

of the lumbar theca was first recognised by Matthews

FIG. 2 Case 1. Oil myelogram showing posteriorlysituated diverticula in the lumbar theca (patient supine).

(1968). They are now regarded as the characteristicmyelographic features in this syndrome (Thomas etal., 1974). They have been recognised more frequentlysince patients have been examined additionally in thesupine position during myelography. They werefound in three of the six cases reported here (cases 1, 3,and 5), in two cases reported by Matthews (1968) andRussell and his colleagues (1968), and in one caseeach of McGill (1966), Rosenkrantz (1971), andThomas et al. (1974). The additional examination ofall patients in the supine position during myelographyis essential for visualisation of diverticula, as posteriorlesions will not fill with the patient prone and couldbe missed easily. This may account for the absence ofdiverticula in some of the reported cases (Table 1).Matthews (1968) described the necropsy findings inone patient in which it was shown that these diver-ticula extended backwards and encroached exten-

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FIG. 3a and b Case 5. Water soluble myelogram showing posteriorly situated diverticula in the lumbar region.

sively on the laminae and spinous process ofa vertebraand eroded the entire posterior surface of the spinalcanal in the lumbosacral region. The role of thesediverticula in the pathogenesis of the cauda equinasyndrome is not clear.The pathogenesis ofankylosing spondylitis remains

unknown (Cruickshank, 1971). Several mechanismsby which the sacral roots could be damaged have beensuggested (Thomas et al., 1974). These are demyelina-tion, interference with blood supply by irradiationand spinal arachnoiditis.

Eleven of the 24 patients in this series and in thosepreviously reported in the world literature (Table 1)had never been treated with radiotherapy (case 3 ofthis study; case I of Bowie and Glasgow, 1961; cases2 and 3 of Hauge, 1961; three cases of Russell et al.,1973; case 1 of Gordon and Yudell, 1973; case 3 ofThomas et al., 1974.) Furthermore delayed post-irradiation myelopathy occurs after about one yearand invariably within five years of irradiation (Zemanand Samorajski, 1971) whereas in all these cases thecauda equina syndrome developed between 17 and

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Cauda equina syndrome in ankylosing spondylitis: a report ofsix cases

40 years after irradiation. Hence delayed post-irradiation effects are unlikely to be the cause of thecauda equina syndrome.

The possibility that spinal arachnoiditis damagesthe roots of the cauda equina may be examined by astudy oftime relations between the onset ofsymptomsand the findings at laminectomy and necropsy(Matthews, 1968). However, laminectomy has beenperformed in only four cases (Hauge, 1961; Lee andWaters, 1962; Gordon and Yudell, 1973) and ne-cropsy in only one case (Matthews, 1968). The densesubarachnoid fibrous tissue described by Hauge(1961) in a patient who underwent a laminectomy oneyear after the onset of symptoms (case 2) contrastedwith the less dense subarachnoid fibrous tissue foundin the patient operated on two years after the onset ofsymptoms. However, no arachnoiditis was found atoperation in the patient described by Lee and Waters(1962) four years after the onset of symptoms or atnecropsy in case 4 of Matthews (1968) ten years afterthe onset of symptoms. Adhesions of nerve roots to adense fibrous arachnoid mater were found at lamin-ectomy in Gordon and Yudell's (1973) third case, butno time relation to the onset of symptoms was stated.Matthews (1968) concluded that arachnoiditis maybe present at the onset of the neurological complica-tions but later becomes inactive or even resolved.This possibility is supported by the raised cerebro-spinal fluid protein in the acute stage of the disease(Boland et al., 1948). Furthermore, most of thereported patients develop their symptoms over a fewmonths and then progress very slowly or not at all.

Another possible mechanism has been postulatedby Matthews (1968). Within the cranium enlargingarachnoid cysts may be formed by arachnoid adhes-ions which form blind pouches into which cerebro-spinal fluid is forced by the pumping action of arterialexpansion (Dott, 1962). If a similar mechanismoperated in the spinal cord and if the bone wereabnormally soft, as suggested by the compression ofthe vertebral bodies by the aorta, diverticula may beformed from localised pressure within the spinalcanal and the sacral nerve roots could be damaged bythe same expansive process. A large arachnoid cystcausing cord compression at a lower dorsal level in apatient with ankylosing spondylitis has been des-cribed (Goldenberg and Logothetis, 1961). Directcompression of nerve by abnormal bony structuresdoes not seem to be the major cause of the caudaequina syndrome as the bony ankylosis does not en-croach on the intervertebral foramina (Thomas et al.,1974). Similar syndromes involving the cauda equinahave been described in other chronic arthropathies.Ramani and Sengupta (1973) have described a caseof tabetic neuroarthropathy of the lumbar spine

causing cauda equina compression with paraplegiaand retention of urine.

Further studies of laminectomy and necropsyfindings are required to unravel the pathogenesis ofthe cauda equina syndrome in ankylosing spondylitis.It is remarkable that von Bechterew postulated theinvolvemenat of the meninges in ankylosing spondy-litis in 1893. The true incidence of the cauda equinasyndrome in ankylosing spondylitis will be deter-mined only by the recognition that symptoms sug-gestive of sacral nerve involvement are not due toinflammation of the sacroiliac joint and that theadditional screening in the supine position is essentialfor the visualisation of the posteriorly situateddiverticula of the lumbar theca by myelography.

I am indebted to the late Dr G. S. Graveson, and toDr J. F. Hallpike and Dr P. K. Robinson for the.radvice and permission to report these cases. I thankDr E. H. Burrows and Dr P. L. Cook for carrying outthe myelography and their useful comments.

REFERENCES

Bechterew, W. von (1893). Streifigheit der Wirbelsauleund ihre Verkummung als besondere Erkrankensform.Neurologisches Centralblatt, 12, 426-434.

Boland, E. W., Headley, N. E., and Hench, D. S. (1948).The CSF fluid in rheumatoid spondylitis. Annals of theRheumatic Diseases, 7, 195-199.

Bowie, E. A., and Glasgow, E. L. (1961). Cauda equinalesions associated with ankylosing spondylitis. Reportof 3 cases. British MedicalJournal, 2, 24-27.

Cruickshank, B. (1971). The pathology of ankylosingspondylitis. Clinical Orthopaedics and Related Research,74,43-58.

Dott, N. (1962). Introductory remarks on hydrocephalus.Developmental Medicine and Child Neurology, 4,259-262.

Goldenberg, G. J., and Logothetis, J. (1961). Neurologi-cal manifestations in 2 cases of ankylosing spondy-litis. Lancet, 1, 448-450.

Gordon, A. L., and Yudell, A. (1973). Cauda equinalesion associated with rheumatoid spondylitis. Annals ofInternalMedicine, 78, 555-557.

Hauge, T. (1961). Chronic rheumatoid polyarthritis andspondylarthritis associated with neurological symptomsand signs occasionally simulating an intraspinal expan-sive process. Acta Chirurgica Scandinavica, 120,395-401.

Lee, M. L., and Waters, D. J. (1962). Neurological com-plications of ankylosing spondylitis. British MedicalJournal, 1,798.

McGill, I. G. (1966). An unusual neurological symptomassociated with ankylosing spandylitis. Guy's HospitalReports, 115,33-36.

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