Hypertrophied Cauda Equina Presenting As Intradural Mass

Spine

Hypertrophied Cauda Equina Presenting As Intradural Mass: Case Report and Review of Literature Michael Hahn, M.D.,* Alan Hirschfeld, M.D., and Howard Sander, M.D.† *Department of Neurosurgery, †Department of Neurology, St. Vincent’s Hospital, New York, New York

Hahn M, Hirschfeld A, Sander H. Hypertrophied cauda equina presenting as intradural mass: case report and review of literature. Surg Neurol 1998;49:514 –9. BACKGROUND

Hereditary motor and sensory neuropathy types I and III usually lead to enlargement of peripheral nerves. Rarely, spinal nerve roots may also be involved, leading to radiculopathy and/or myelopathy. METHODS

This 44-year-old man with back and lower extremity radicular pain and distal lower extremity weakness and numbness was found to have a nonenhancing intradural mass that caused a nearly complete myelographic block from L1–L4. He underwent a decompressive laminectomy with intradural exploration. RESULTS

Hypertrophic but otherwise normal-looking nerve roots were observed. Subsequent electrodiagnostic testing and sural nerve biopsy confirmed that this patient had a previously unsuspected hereditary motor and sensory neuropathy (HMSN). His pain resolved, but at latest follow-up his weakness and numbness persisted. CONCLUSIONS

Nonenhancing spinal intradural mass lesions may represent enlarged nerve roots, which have a number of potential etiologies. Electrodiagnostic studies and peripheral nerve biopsy are instrumental in establishing the diagnosis of HMSN. © 1998 by Elsevier Science Inc. KEY WORDS

Cauda equina, nerve roots, hereditary motor and sensory neuropathy.

ypertrophic neuropathy is an uncommon etiology of spinal intradural mass lesions. Processes that lead to hypertrophic neuropathy include acromegaly, amyloidosis, Refsum’s disease,

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Address reprint requests to: Alan Hirschfeld, M.D., Department of Neurosurgery, St. Vincent’s Hospital and Medical Center of New York, 153 West 11th Street, New York, NY 10011. Received September 11, 1996; accepted February 5, 1997. 0090-3019/98/$19.00 PII S0090-3019(97)00160-2

leprosy, neurofibromatosis, chronic inflammatory demyelinating polyradiculoneuropathy syndrome, and hereditary motor and sensory neuropathies type I [Charcot-Marie-Tooth (CMT) disease], and type III [Dejerine-Sottas (DS) disease] [1]. These processes only rarely cause symptomatic spinal nerve root enlargement. This occurs so infrequently that, when central nervous system (CNS) dysfunction is encountered, even in an individual with known hereditary motor and sensory neuropathy (HMSN), other etiologies such as spondylotic, infectious, granulomatous, and neoplastic diseases are usually considered. We report a patient with no previous neurologic complaints, who presented with progressive back and leg pain, leg weakness and numbness, and an intradural mass on both magnetic resonance imaging (MRI) and myelography.

Case Report This 44-year-old right-handed white man presented with a 3-month history of progressive low back and bilateral leg pain, and distal lower extremity numbness and weakness. The pain tended to be worse at night and when he laid down. The patient denied bowel or bladder dysfunction. Three months prior to the onset of symptoms, he had been struck on the head by a falling concrete block. No loss of consciousness was reported, but he had fallen onto his buttocks. Physical examination revealed an obese white man with profound bilateral tibialis anterior, tibialis posterior, and extensor hallucis longus weakness, patchy deficits to pin prick sensation from L4 –S1, and loss of proprioception and vibration sense at the ankles. Sacral sensation was only mildly affected © 1998 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010

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T2-weighted (left) and T1weighted postenhancement (right) sagittal MRI showing filling of the thecal sac from the bottom of L1 to the top of L5 with nonenhancing soft tissue mass.

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and there was no significant gastrocnemius, hamstring, quadriceps, or ileopsoas weakness. His Achilles and patellar tendon reflexes were absent bilaterally. MRI of the lumbar spine showed a nonenhancing mass filling the thecal sac from L1–L4, which was isointense to spinal cord on all sequences (Figure 1). There was also mild posterior scalloping of several vertebral bodies and a slight compression fracture of L1 that was attributed to his prior trauma. Because of difficulty in performing a myelogram via lumbar puncture, a C1–2 myelogram was performed, followed by computerized tomography (CT). A protein level of 133 was the only CSF abnormality. The myelogram showed a nearly complete block with a “paint-brush” appearance, at L1 (Figure 2A), and the CT demonstrated specks of contrast material within the mass (Figure 2B), felt to possibly represent the interstices between enlarged nerve roots. Due to an enlarged hilar lymph node on chest X ray and CT scan, sarcoidosis was also considered in the differential diagnosis, which included arachnoiditis, hemorrhage from previous trauma, and neoplasia.

Due to the patient’s severe, progressive neurologic deficits, a decompressive laminectomy of L4 and L5 was performed at this time. Upon opening the dura and arachnoid, the nerve roots of the cauda equina were found to be markedly thickened and enlarged, but otherwise healthy in appearance (Figure 3). No further pathology was noted, and, after releasing CSF from both above and below the dural incision, the dura could be closed easily. Postoperatively, the patient reported near complete resolution of his back pain and some improvement in his ability to walk. However, his numbness and weakness did not objectively improve. A diagnosis of HMSN was postulated, and, upon questioning, one of the patient’s older relatives revealed that several family members had had a variety of unexplained foot abnormalities and neurologic symptoms. Electrodiagnostic studies were then performed. Lower extremity sensory and motor, and upper extremity sensory nerve conduction potentials were absent or had very low amplitudes. Upper extremity motor nerve conduction potentials revealed severe slowing (approximately 10 m/s) with a moderate decrease in amplitudes and little

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(A) Anteroposterior view from C1-2 injection myelogram, showing widening of thecal sac starting at T-12, and blockage of contrast flow below L2; (B) Postmyelogram CT image at L1, showing specks of contrast within soft tissue intradural mass.

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temporal dispersion upon distal stimulation. Needle electromyography revealed fibrillation potentials and neuropathic motor units in bilateral distal leg and also gluteus medius and biceps femoris (short head) muscles. Proximal S1-innervated muscles, upper extremity and paraspinal muscles above the surgical site were normal. These findings are most consistent with a demyelinating HMSN, with secondary axonal degeneration, as well as superimposed bilateral L5 radiculopathies. A hereditary etiology of the polyneuropathy is suggested by the lack of temporal dispersion (Figure 4). The patient’s left sural nerve was biopsied. Pathologic findings revealed a hypertrophic neuropathy

with “onion bulb” formation, fibrocyte proliferation, and increased endoneurial collagen consistent with HMSN type I. A negative blood test for CMT-specific junction fragment duplication on chromosome 17p ruled out a diagnosis of the IA variant of CMT disease. Examination of the patient revealed palpably thickened superficial radial nerves at the wrists, and ulnar nerves at the elbows. At his 1 month follow-up visit, the patient reported a significant relief of his back and leg pain with improved ambulation. Physical examination did not reveal any objective improvement in his sensory or motor findings. The patient’s sister, age 34 years, was subsequently evaluated electrodiagnostically. She

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Intraoperative photograph, showing thickened nerve roots extruding through arachnoid incision.

had diffuse, severe nerve conduction slowing in both upper and lower extremities, with minimal temporal dispersion and no denervation on needle electromyography, clearly confirming a hereditary demyelinating neuropathy.

Discussion CMT disease, also known as hereditary motor sensory neuropathy, type I, is characterized by peripheral nerve enlargement, muscle weakness and atrophy, foot deformities such as pes cavus, and pathologic findings of segmental demyelination and attempted remyelination, leading to so-called “onion bulb” formation [2]. The most common variant, HMSN-IA, is inherited in an autosomal dominant fashion, is generally milder than other variants, and is associated with a chromosome 17p duplication that is detectable by a commercially available blood test [2]. The product of this gene is peripheral myelin protein 22. Another variant, HMSN-IB, is associated with a chromosome 1q defect, linked to the Duffy blood group locus. HMSN IC and ID have also been described. Dejerine-Sottas (DS) disease, or HMSN type III, also typically presents with hypertrophied peripheral nerves. The diagnosis of HMSN I or III is usually based upon peripheral nerve biopsy findings, and on electrodiagnostic studies [2]. The latter show severely slowed conduction velocities indicating peripheral nerve demyelination. In addition there is a relative preservation of waveform morphology (little temporal dispersion) indicating a diffuse, uniform demyelination of all nerve fibers, which is characteristic of a hereditary etiology. With increasing severity of illness, the responses become absent and fibrillation potentials appear on needle electromyography indicating secondary axonal degeneration,

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which causes the majority of the patient’s clinical symptomatology. It is quite rare for patients with HMSN to present with CNS manifestations. Carlin et al. [1] reviewed six cases of “hypertrophic interstitial neuritis” reported prior to 1982, which had presented with radiculopathy or myelopathy, and myelographic evidence of enlarged nerve roots and partial or complete cerebrospinal fluid (CSF) blocks. Since then, to our knowledge, eight such cases with CMT disease and two with DS disease, have been reported [3–5,7,8,11,12]. In roughly one-half of these patients, the diagnosis of HMSN had not been made prior to the onset of CNS findings. Although standard MRI sequences and lack of enhancement with gadolinium may lead one to suspect hypertrophied nerve roots, the use of fast spin echo sequences [3], or the visualization of contrast interspersed within an otherwise homogenous mass after myelography, is even more suggestive of this entity. Other radiographic features include scalloping of the posterior border of lumbar vertebral bodies, and widening of multiple intervertebral foramina. Other entities that cause homogeneous intradural masses generally enhance with contrast [6]. Even cystic tumors display enhancement around their rims [10]. Arachnoiditis and sarcoidosis, which were considered as potential diagnoses in our patient, usually enhance. Two entities that do not enhance are intradural collections of blood [14] and the redundant nerve root syndrome first described by Verbeist in 1951 [15], and more recently reported by Suzuki et al. [13], and Naguib et al. [9]. In the former, one would

Left ulnar motor nerve conduction study recording over the hypothenar eminence and with stimulation (top to bottom) at the wrist and below the elbow. There is severe slowing of nerve conduction (12 m/s) with relative preservation of waveform morphology suggesting a hereditary demyelinating neuropathy.

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not expect the mass to be isointense to spinal cord on all sequences, and in the latter, there is often a concomitant lumbar canal stenosis. The elevated CSF protein found in most patients with HMSN involving the spinal nerve roots is nonspecific, and does not help to establish this diagnosis. In the patient presented here, there were several factors that hindered our making the correct diagnosis preoperatively. The first was our initial failure to elicit a family history of neurologic problems or to detect the patient’s palpably enlarged peripheral nerves. The second factor was the recent history of trauma to the head and buttocks, with evidence of axial loading forces causing a compression fracture of L1. The third factor was the abnormality seen in the chest X ray and CT scan that was suggestive of sarcoidosis. The majority of reported cases of HMSN leading to hypertrophic nerve roots do not mention surgical therapy or its results. In those patients who have undergone surgery, it has usually consisted of multilevel laminectomies with dural patch grafting to decrease the constriction caused by a confining intact dura. Results have not always been excellent, but what improvement has been obtained may have been due to release of pressure on the vasculature of the hypertrophied nerve roots. The pain relief noted by the patient in this report may be attributable to decompression of his L5 roots that were clearly abnormal on electrophysiologic testing.

REFERENCES 1. Carlin L, Biller J, Challa V, Riela A. Hypertrophic neuropathy with spinal cord compression. Surg Neurol 1982;18:237– 40. 2. Dyck PJ, Thomas PK, Griffin JW, Low PA, Poduslo JF. Peripheral neuropathy. Philadelphia: WB Saunders, 1993:1094 –136. 3. Friedman DP, Flanders AE, Tartaglino LM. Hypertrophic Charcot-Marie-Tooth disease: MR imaging findings. AJR 1994;163:749 –50. 4. Kremenitzer M, Ager PJ, Zingesser LH. Myelographic evidence for nerve root enlargement in a case of Charcot-Marie-Tooth disease. Neuroradiology 1976; 11:165–7. 5. Masuda N, Hayashi H, Tanabe H. Nerve root and sciatic trunk enlargement in Dejerine-Sattas disease: MRI appearance. Neuroradiology 1992;35:36 –7. 6. Matthew P, Todd NV. Intradural conus and cauda equina tumors: a retrospective review of presentation, diagnosis and early outcome. J Neurol Neurosurg Psychiatry 1993;56:69 –74. 7. Miura T, Hirabuki N, Imakita S, Harada K, Kawai R, Mitomo M, Takahashi M. Radiological findings in a case of Charcot-Marie-Tooth disease. Br J Radiol 1985;58:1017–20.

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8. Morano JU, Russell WF. Nerve root enlargement in Charcot-Marie-Tooth disease: CT appearance. Radiology 1986;161:789. 9. Naguib MG, Latchaw RE, Erickson DL, Seljeskog EL. Redundant nerve roots of the cauda equina. Neurosurgery 1981;9:444 –9. 10. Penisson-Besnier I, Guy G, Gandon Y. Intramedullary epidermoid cyst evaluated by computed tomographic scan and magnetic resonance imaging: case report. Neurosurgery 1988;25:955–9. 11. Petrela M, Xhumari A, Buda L, Kuqo A, Baboc¸i H. Compression du cone terminale et forme hypertrophique de la maladie de Charcot-Marie. Rev Neurol (Paris) 1991;147:397–9. 12. Rosen SA, Wang H, Cornblath DR, Uematsu S, Hurko O. Compression syndromes due to hypertrophic nerve roots in hereditary motor sensory neuropathy type I. Neurology 1989;39:1173–7. 13. Suzuki K, Takatsu T, Inoue H, Teramoto T, Ishida Y, Ohmori K. Redundant nerve roots of the cauda equina caused by lumbar spinal canal stenosis. Spine 1992;17:1337– 42. 14. Willems J, Anne´ A, Herregods P, Klaes R, Chappel R. A Cauda equina syndrome in a patient treated with oral anticoagulants. Paraplegia 1994;32:277– 80. 15. Verbiest H. Unusual forms of compression of the cauda equina. Presented at the LUSO Spanish Society and the British Society meeting of Neurological Surgeons, Madrid, Spain. 1951.

COMMENTARY

This is certainly a rare and very unusual entity. I have heard from other colleagues of enlarged spinal nerve roots that on biopsy have proven to have “onion whorl” or hypertrophic neuropathic changes. These, though have usually been solitary root(s) and not the entire cauda equina, as is so documented in this case. Hypertrophic neuropathy or “onion bulb” or “whorl” change can affect peripheral nerves and be unassociated with CMT disease or DS disease, or other causes of nerve enlargement such as amyloidosis or Hansen’s disease. This type of localized hereditary neuropathy is not at the present time felt to be genetically linked. Loss of function is usually progressive but can sometimes be partially reversed by resection of the abnormal segment of nerve and graft repair. Such, of course, would not seem practical here where all of the cauda equina was so extensively involved. The case presented does show an MRI disc and spondylitic changes at multiple levels, but these changes do not seem to provide enough stenosis to account for an irritative change in all of the cauda equina, so the process was primary to nerve(s). This was well corroborated by subsequently attaining a family history compatible with hereditary neuropathy, the very abnormal conductive studies on

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both upper and lower extremity nerves, enlarged peripheral nerves on examination, and a sural nerve biopsy that showed hypertrophic “onion bulb” changes. Should a similar situation be encountered in the future, I think one is justified in decompressing the cauda equina, verifying a root change by biopsy, and then considering whether “expansion” of the caudal sac by means of a dural graft is in-

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dicated. Unfortunately, functional loss, although slowed down, may still progress and pain, although initially relieved, may recur. David G. Kline, M.D. Neurosurgery Department Louisiana State University Medical Center New Orleans, Louisiana

ven if a teenager has no intention to start smoking, tobacco advertising and promotional items can lead one-third of them to try, according to an article in the February 18 issue of the Journal of the American Medical Association (JAMA). John P. Pierce, Ph.D., from the University of California, San Diego, in La Jolla, and colleagues conducted the first longitudinal study on the effect of cigarette promotion on teenagers. In 1993, they interviewed 1752 California adolescents (age 12 to 17 years old) who had never smoked and who had said they had no plans to start smoking, even if a friend offers them a cigarette. The adolescents were reinterviewed in 1996. They write: “From these data, we estimate that 34 percent of all experimentation in California between 1993 and 1996 can be attributed to tobacco promotional activities. . . . “This longitudinal study provides clear evidence that tobacco industry advertising and promotional activities can influence nonsusceptible never smokers to start the process of becoming addicted to cigarettes. . . . Our data establish that the influence of tobacco promotional activities was present before adolescents showed any susceptibility to become smokers.”

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—AMA Press Release February 17, 1998