The role of sensory and motor evoked potentials in the prognosis of Pott's paraplegia

Abstract

Objective: In view of paucity of evoked potential changes in Pott's paraplegia, it is proposed to evaluate the role of motor and somatosensory evoked potentials in predicting the outcome.

Methods: Consecutive patients with Pott's paraplegia during 1993-2003 were subjected to detailed clinical, radiological and evoked potential study. The latter comprised of tibial somatosensory evoked potential (SEP) and motor evoked potential (MEP) study to tibialis anterior. The patients were clinically evaluated at 6 and 12 months and the outcome was defined into poor (bed ridden), partial (dependent for activities of daily living) and complete recovery (independent). The evoked potential findings were correlated with clinical and radiological findings and outcome.

Results: There were 39 patients whose age ranged between 16 and 70 (mean 42.1) years and 22 were females. The mean duration of symptoms was 8.2 months. Sensory motor deficit was present in 18 and pure motor signs in 21 patients. Five patients had quadriplegia and remaining had paraplegia. The muscle weakness was severe in 12 and moderate in 15 patients. In 12 patients, lower limb power was normal but they had lower limb hyper-reflexia with or without spasticity suggesting pyramidal dysfunction. Pinprick and joint position sensations were abnormal in 18 patients. MRI was abnormal in all and revealed cervical involvement in 7, thoracic in 22 and lumbar in 10 patients. Paravertebral soft tissue shadow was present in 36 and cord compression in 30 patients. Motor evoked potential was abnormal in 19 patients (unrecordable in 11 patients, 21 sides and prolonged in 8 patients, 14 sides). SEP was abnormal in 18 patients (unrecordable in 15 patients, 25 sides and prolonged central conduction in 8 patients, 9 sides). Both MEP and SEP were abnormal in 16, normal in 18, and only MEP was abnormal in 3 and only SEP in 2 patients. At 6 month 25 patients had complete, 9 partial and 5 poor recovery. At 1 year 33 had complete and 4 partial recovery. SEP and MEP abnormalities correlated with respective sensory and motor functions, vertebral level and outcome at 6 and 12 months.

Conclusions: MEP and SEP both are helpful in predicting 6-month outcome. Combining SEP and MEP gives stronger correlation with 6-month outcome compared to only MEP or SEP. The potential role of evoked potentials in deciding different therapeutic strategies needs further studies.