Case of the Week

Intradural extramedullary Tuberculosis of spine

(Tubercular radiculomyelitis)

A 25 year old lady presented with complaints of progressive weakness in the lower limb of 1 month duration. At the time of presentation she was unable to sit without support and had developed urinary incontinence two days before. She had fallen from bed few days before the onset of symptoms. 4 months back she had developed headache and weakness in all four limbs. She had been hospitalised, evaluated and diagnosed to have tubercular meningitis. Treatment was started and she had improved with normalization of power in the lower limb and improving power in the upper limb.

On presentation she was incoherent and had dysarthria. She had grade 5/5 power in the left upper limb, grade 3/5 power in proximal and grade 0/5 power in intrinsics of right upper limb, grade 4/5 power in the left lower limb and grade 2-3/5 power in right lower limb. Sensory impairment was present from L2. Reflexes were absent and plantar response was extensor.

X rays of the spine were normal. MRI of the spine revealed an intradural enhancing mass at L2-L4 region. The nerve roots were thickened and adherent suggestive of arachnoiditis. Skeleton was unaffected. CT scan of the brain revealed hydrocephalus.

Taking into consideration recent history of tubercular meningitis, diagnosis of intradural extramedullary (IDEM) tuberculoma was made. Ventricular shunting was done for hydrocephalus. L2-L4 laminectomy and durotomy was done to explore the mass, which was found completely encircling the nerve roots and adherent to the arachnoid. Mass contained within loculated caseous material. The mass was entirely removed with microscopic dissection and dura was repaired. Diagnosis of tuberculosis was confirmed by histopathology.

Postoperatively antitubercular therapy was reinstituted with addition of steroids. Postoperative period was uneventful. There was improvement in the power of limbs and patient was walking with support ten days after the surgery.

Tuberculosis of the spine is the most common form of skeletal tuberculosis. The affliction is in the form of tubercular spondylitis, intradural tuberculosis and tubercular myelitis in decreasing frequency. Involvement of the spinal cord in the absence of skeletal lesion is uncommon and around hundred cases are reported in various series and case reports. However intradural tuberculosis preceded by meningitis is extremely rare and only few cases have been reported. IDEM has been reported few days to 20 years after diagnosis of meningitis.Isolated IDEM tuberculosis is commonly seen in thoracic spine and presents as gradually progressive weakness in the lower limbs, sometimes associated with urinary symptoms.

However, IDEM Tb with tubercular meningitis has varied presentations. Some patients after showing good response for antitubercular therapy for meningitis suddenly deteriorate. This is termed as paradoxical reaction and is a well-known complication of treatment of Tb meningitis. This is caused by enlargement of existing lesion or development of new lesions. Various mechanisms have been suggested to be causing paradoxical reaction. Most widely accepted theory is reactivation of depressed cellular immunity with successful antitubercular therapy. The enlargement of preexisting lesion is caused by enhanced immunological reaction and new lesions develop at the site of seeding of tubercular bacilli and its products. Similar reaction may lead to manifestation of IDEM Tb as coexisting lesion may be present in the spinal cord or may develop later due to seding. Tubercular bacilli are usually demonstrated in these cases.

Cases presenting late show features of arachnoiditis and myelomalacia with syrinx formation and probably represent late ischaemic changes in the cord in previously asymptomatic IDEM Tb. No active tuberculosis has been demonstrated in such patients who have fully completed therapy.

Despite apparent deterioration, the clinical picture is not to be confused with drug resistance as all these patients respond well with continuation of same drugs. Although there are no prospective trials, use of steroids is strongly recommended in these patients to reduce the inflammatory reaction. Features of cord compression warrant early surgical decompression of the mass. Recovery is usually good but may not be complete owing to ischaemic changes and obstruction to CSF flow. However, cases presenting late respond poorly to surgical decompression and guarded prognosis should be given regarding outcome.