A patient with symptoms and signs of lumbar canal stenosis showed non-malignant, nerve root hypertrophy on MRI. The patient responded dramatically but temporarily to intravenous immunoglobulin (IVIg).

Hypertrophy of nerve roots is recognised as a cause of “spinal stenosis” syndrome.1 The association has been previously described with hereditary causes such as neurofibromatosis, Refsum’s disease, and hereditary motor and sensory neuropathy (HSMN) type 1 and 3.2 There have been recent reports of chronic inflammatory demyelinating polyneuropathy (CIDP) presenting as a spinal stenosis syndrome.1 3 We report on a patient with an acquired inflammatory radiculopathy who presented with a lumbar canal stenosis syndrome only responsive to IVIg.

A 60 year old white man presented with a 2 year history of progressive numbness and stiffness of his legs with difficulty in walking. He had noticed the discomfort in his legs to be exacerbated after walking 100 metres and relieved by rest. He could cycle long distances without discomfort. He specifically denied any upper limb symptoms or sphincter disturbance. He had mild hypertension treated with nifedipine. There was no relevant family history.

Examination of the cranial nerves and upper limbs was normal. In the lower limbs there was symmetric wasting of the extensor digitorum brevis with grade 4/5 weakness of ankle dorsiflexion, eversion, and big toe extensors. Deep tendon reflexes were absent in the lower limbs. The plantar responses were flexor. Sensory examination disclosed pin prick, soft touch, and vibration sense to be reduced to knee level. Joint position sense was preserved.

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MRI of the lumbar spine showing ill defined hypertrophic nerve roots (black arrow).

Routine haematological and biochemical investigations were normal and there was no serum paraprotein. Prostate specific antigen, vitamin B₁₂, venereal laboratory research test, and HIV serology were negative. Enzyme linked immunosorbent assay (ELISA) Ig forBurgdorferi was negative. Plain radiology of the chest and lumbar sacral spine was normal. Intial CSF examination disclosed a raised protein of 2.08 g/l, glucose 3.7 mmol/l, and a white cell count of 40 cells/mm³ (75% reactive lymphocytes). Cytology was normal. CSF angiotensin converting enzyme concentration was normal and acid fast bacilli culture negative. Nerve conduction studies and EMG showed dispersed F wave responses (right common peroneal 49–88 ms and right posterior tibial nerve 45–80 ms) together with denervation in the right tibialis anterior. Motor conduction velocities in the limbs were normal with preserved sensory action potentials. Lumbar spine MRI showed poorly defined hypertrophic nerve roots (figure).

On exploration of the intradural contents , the roots were “matted together” and not free floating in the CSF. Biopsies were taken of the ligamentum flavum, dura, and arachnoid, and this showed a mixed population of inflammatory cells in the ligamentum flavum sections. Examination of CSF on this occasion showed the same protein concentration of 2.08 g/l and a white cell count of 2 cells/mm³.

Oral prednisolone (40 mg/day) caused a deterioration in his symptoms. The patient was given a 5 day course of IVIg (0.4 g/kg/day) and made a dramatic recovery and within 3 days the motor and sensory examination was normal but the knee and ankle jerks were still absent. Treatment with IVIg provides clinical benefit lasting 2–3 weeks, and neither this pattern nor the dose of IVIg prescribed has been altered by giving azathioprine, cyclophosphamide, or cyclosporin.

The patient presented with an acquired, non-malignant, root hypertrophy. There are electrical features to suggest this may be a CIDP, although the reactive CSF showed a higher white cell count than usual,4 5 subsequent CSF white cell counts have been normal. Unlike previous cases of CIDP the root hypertrophy described in our patient has shown no benefit after oral immunosuppresion. Indeed, introduction of a moderately high dose of prednisolone caused a dramatic deterioration, a response that is recognised in CIDP.3 6 Unlike the modest clinical benefit seen by others after the adminstration of IVIg3 our patient remains exquisitely sensitive to IVIg.