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Serial somatosensory and brainstem auditory evoked potentials in monitoring of acute supratentorial mass lesions.

OBJECTIVE
To determine the relevance of serial evoked potentials (brainstem auditory evoked potentials and somatosensory evoked potentials) and clinical parameters (pupillary response and intracranial pressure) in patients with acute supratentorial mass lesions.


DESIGN
Prospective case series of comatose patients with acute supratentorial mass lesions.


SETTING
Neurocritical care unit of a tertiary care center.


PATIENTS
Thirty consecutive patients with the following study inclusion criteria: a) clinical and computed tomography evidence of an acute supratentorial mass lesion; b) implantation of an intracranial pressure monitoring device; and c) a persistent comatose state during the observation period.


INTERVENTIONS
Brainstem auditory evoked potentials, somatosensory evoked potentials, intracranial pressure, and pupillary responses were recorded at the time of three particular events: a) immediately after implantation of an epidural intracranial pressure monitoring device; b) during intracranial pressure therapy; and c) at termination of intracranial pressure therapy. Evoked potential results were ranked into three categories: a) normal on both sides; b) abnormal or absent on one side; and c) evoked potentials on both sides abnormal or absent. Spearman's rank correlation was performed to analyze serial recordings. Cross tables were generated to determine the prognostic value of evoked potentials and clinical parameters. Fisher's exact test was applied to calculate statistical significance.


MEASUREMENTS AND MAIN RESULTS
Intracranial pressure values correlated with pupillary responses and brainstem auditory evoked potentials during and at the termination of intracranial pressure therapy. Pupillary findings correlated with brainstem auditory evoked potentials only at the time of termination of intracranial pressure therapy. There was no correlation between somatosensory evoked potentials and clinical parameters. Pupillary responses indicated a good or poor recovery during and at the termination of intracranial pressure therapy. Brainstem auditory evoked potentials and intracranial pressure values distinguished between good and poor outcome only at termination of intracranial pressure therapy. Somatosensory evoked potential results did not predict outcome.


CONCLUSIONS
Shortly after manifestation of supratentorial mass lesions, the results of evoked potentials and clinical parameters indicate increased intracranial pressure and incipient transtentorial herniation but do not predict sequelae. Our results indicate that after institution of effective therapy, pupillary abnormalities and brainstem auditory evoked potentials serve as valuable prognostic predictors. In contrast, somatosensory evoked potentials reflect neither therapeutic efficacy nor outcome in our patient population.