Tuberculous Myelitis

Tuberculous myelitis is spinal cord involvement by Mycobacterium tuberculosis without vertebral collapse. It includes tuberculous radiculomyelitis (arachnoiditis), intramedullary tuberculoma and syrinx, and accounts for a small share of spinal tuberculosis. It occurs in people with tuberculous meningitis or from adjacent spinal disease.

Pathophysiology. A thick basal and spinal exudate causes arachnoiditis, vasculitis and cord ischaemia, with compression of nerve roots. Tuberculoma forms inside the cord.

Subacute paraparesis or quadriparesis, radicular pain, sensory level, bladder and bowel dysfunction, and loss of reflexes with a flaccid pattern in arachnoiditis. Fever, weight loss, night sweats and headache or cranial nerve palsies may indicate tuberculous meningitis.

Red flags.

• Progressive paraparesis in a patient from an endemic area or with tuberculosis exposure.
• Rapid deterioration or bladder involvement.

MRI of the spine with contrast shows leptomeningeal thickening and enhancement, cord swelling, intramedullary ring enhancing lesions, syrinx or loculated cerebrospinal fluid. CSF shows lymphocytic pleocytosis, raised protein and low glucose, with nucleic acid amplification testing for the organism and culture. Chest imaging and sputum tests. HIV testing is essential. Biopsy of a lesion if the diagnosis is unclear.

Differential diagnosis.

• Neuromyelitis optica spectrum disorder and transverse myelitis.
• Spinal cord tumour, sarcoidosis and lymphoma.
• Neuroschistosomiasis and neurosyphilis.

Anti-tuberculosis therapy. Intensive phase for 2 months with isoniazid 5 mg/kg (maximum 300 mg), rifampicin 10 mg/kg (maximum 600 mg), pyrazinamide 25 mg/kg (maximum 2 g) and ethambutol 15 mg/kg (maximum 1.2 g) daily. Continuation with isoniazid and rifampicin to complete 9 to 12 months. Give pyridoxine 10 to 25 mg daily with isoniazid. Adjust for drug resistance.

Corticosteroids. Dexamethasone 0.4 mg/kg daily IV (maximum 12 mg), reduced over 6 to 8 weeks, or prednisolone 1 mg/kg daily, to reduce inflammation and arachnoiditis.

Surgery. Decompression for cord compression or large tuberculoma, shunt for hydrocephalus, and drainage of a syrinx in selected patients.

HIV. Start antiretroviral therapy 2 to 8 weeks after antituberculosis therapy (earlier with CD4 count under 50 cells/microlitre, but delay if meningitis). Watch for paradoxical reactions.

Rehabilitation. Physiotherapy, bladder care, pressure care and venous thromboembolism prophylaxis.

Monitoring. Liver tests at baseline and every 2 to 4 weeks, visual acuity on ethambutol, adherence and repeat MRI at 3 months.

Referral and escalation. Refer to infectious diseases, neurology and neurosurgery.

Special groups. In pregnancy, give the same first line drugs, with pyridoxine.