Diplopia and strabismus convergens mimicking symptoms of tuberculous meningitis as side-effects of isoniazid

Abstract

Tuberculosis remains the most frequent infectious cause of death in the world, has re-emerged in developed nations, and demonstrates a steady increase in incidence in children [1,7,10]. Extra-pulmonary disease has also increased and tuberculous meningitis is one of the presentations with a high morbidity and mortality [1,7]. Symptoms of tuberculous meningitis are not very specific and may include weight loss, fatigue, rigidity and signs of cranial nerve palsy [7]. Early diagnosis of tuberculous meningitis is essential for the cure of children and/or the prevention of neurological deficits.A 7-year-old boy presented at the outpatient clinic of the Department of Ophthalmology of our hospital with complaints of strabismus convergens and horizontal diplopia. For 6 weeks he was known to doctors of the Agency for Tuberculosis Control because of a strongly positive Mantoux test (18 mm swelling with induration and redness) but a normal chest X-ray film. These investigations were carried out because his stepfather appeared to have active lung tuberculosis. Our case had not received a BCG vaccination in the past. The boy was treated with isoniazid prophylaxis for 6 weeks at a daily dose of 150 mg (5 mg/kg). He did not use other drugs. The boy's younger brother had enlarged lymph nodes on a chest X-ray film and was treated with four tuberculostatic agents.Ophthalmological evaluation of our patient showed a left-sided abducens palsy, no movement of redress on cover-and uncover testing and bilateral haziness of the optic discs. Visual acuity was normal. Further physical and neurological examination showed discrete neck stifness. However, examination of the other cranial nerves was normal and no disturbances in muscle tone and strength, coordination, sensibility, and tendon reflexes were observed. He had no enlarged lymph nodes and lung auscultation was normal. His height was 132 cm (+1 SDS) and weight 30.7 kg (+1 SDS). To exclude a tuberculous meningitis or an intracerebral tuberculoma, he underwent MRI of the brain followed by a lumbar puncture. The MRI scan demonstrated no abnormalities: no elevated intracranial pressure, no tumour and no signs of basal meningitis. Lumbar puncture showed a normal pressure (17 cm H 2 O). The results of the CSF analysis were: 2 leucocytes/ll (66% lymphocytes, 29% granulocytes, 4% monocytes), glucose 4.0 mmol/l, protein 0.34 g/l (slightly elevated), chloride 123 mmol/l, and lactate 1.9 mmol/l. ZiehlNeelsen staining of the CSF was negative. Culture demonstrated no growth of Mycobacterium tuberculosis or growth of other possible bacterial or viral pathogens. Liver enzymes (serum alanine aminotransferase, glutamate pyruvate transaminase, alkaline phosphatase, gamma-glutamyl transpeptidase, lactate dehydrogenase) were normal. On basis of these findings, (tuberculous) meningitis with raised intracranial pressure was excluded. Finally, we considered the possibility that isoniazid was responsible for the neurological abnormalities [3,7]. Isoniazid was stopped and replaced by rifampicine and pyridoxin...