Speech brain mapping by direct cortical stimulation during the awake craniotomy and possible increase in sympathetic activity: a case report

ABSTRACT
Background: During the last three years awake craniotomy (AC) was successfully implemented in Croatia, using monitored anaesthetic care (MAC) as anaesthetic technique. Patient was a 44-year-old female with an expansive tumor in the left fronto-temporal cortex. Mapping of primary motor cortex (M1) and Broca’s area was performed by direct cortical stimulation (DCS) during AC. We were monitoring the change of vital parameters during speech brain mapping intraoperatively in awake patient.
Case report: The patient was sedated and breathed spontaneously during the procedure. We used target controlled infusion pumps for fine titration of remifentanil and propofol with local infiltration at the site of pin insertion, skin incision and nerve blocks. The DCS paradigm of 5 monophasic pulses of 0.4 ms duration, repetition rate of 2.2 Hz, intensity up to 15 mA was used over the left primary motor cortex and over the Broca’s area. The corticobulbar motor evoked potentials (CoMEPs) were recorded from laryngeal muscles as short latency responses (SLR), while long latency responses (LLR) were elicited by premotor cortex mapping in the caudal opercular part of inferior frontal gyrus, including Broca’s area. During the DCS, patient’s clinical response was video recorded and correlated with continuously monitored invasive BP and HR.
Discussion: During DCS that elicited the response of M1 for laryngeal muscles, CoMEP with SLR of 5.62 ms was recorded, and the patient developed clinical picture of dysarthria / anarthria. During that period patient’s BP and HR were unchanged. During DCS mapping of premotor cortex in the caudal opercular part of inferior frontal gyrus, including Broca’s area, patient manifested clinical onset of verbal paraphasia and speech arrest, recorded as the CoMEPs with LLR of 37.4 ms. Ten minutes after the symptoms onset, the BP increased 20 mmHg. Five to seven minutes after BP change, HR increased 10 to 15 bpm. The raising pattern of BP and HR was detected each time when severe central motor speech deficit was induced by DCS.
Conclusion: We had successfully performed mapping of Broca’s area, as a part of AC. During the DCS, the clinical signs of central motor speech - the significant central failure in speech tasks - were accompanied by raising in BP and HR, as indication of possible onset of increased sympathetic activity. This should be kept in mind because of potentially life-threatening conditions accompanied by increased sympathetic activity.