Motor and somatosensory evoked potentials in tuberculous meningitis: a clinico-radiological correlation

Objective - The sensory and motor functions in severe tuberculous meningitis (TBM) may be difficult to assess clinically and may be helped by evoked potential studies. Lack of motor and somatosensory evoked potential studies in TBM prompted the present study. Methods - All the patients with TBM underwent detailed neurological evaluation and cranial CT scan study. Motor and somatosensory evoked potentials to both upper and lower limbs were carried out bilaterally. The outcome was defined on the basis of 3 month Barthel Index (BI) score into good (BI greater than or equal to 12) and poor (BI<12). Results - Forty-one highly probable patients with TBM whose ages ranged between 8 and 64 years and 14 of whom were females were included in this study. Twenty-three patients were in stage III (meningitis, neurological signs and altered sensorium), 12 in stage II (meningitis with neurological sign) and the remaining patients were in stage I (meningitis only). Cranial CT scan was carried out in all and MRI in 18 patients. On CT scan hydrocephalus was present in 21, infarction in 14 and tuberculoma in 4 patients. Motor evoked potential (MEP) was abnormal in 18 patients (36 limbs) and SEP in 9 patients (23 limbs). Upper limb central motor conduction time to abductor digiti minimi (CMCT-ADM) was abnormal in 15 and that to tibialis anterior (TA) in 21 limbs. CMCT abnormality was lateralized in 6 and only upper or lower limbs were involved in 11 patients. The SEP abnormalities were lateralized in 2 patients and only upper or lower limbs were involved in 3. The MEP changes correlated with stage of TBM and outcome whereas SEP with outcome only. Conclusion - Motor and somatosensory evoked potentials may be helpful in objective documentation of respective motor and sensory functions in TBM patients with altered sensorium.