Akinetic mutism reversed by inferior parietal lobule repetitive theta burst stimulation: Can we restore default mode network function for therapeutic benefit?

Abstract

Background: Transcranial magnetic stimulation is a noninvasive treatment used to modulate cortical excitability. Its use over the last two decades has expanded, ranging from psychiatric disorders to traumatic brain injury and poststroke rehabilitation.

Objectives: We present the case of a 59-year-old male patient who presented in a decreased state of consciousness due to a right frontal glioblastoma, wherein his state was not improved by a successful surgery and could not be explained by any other condition. Due to his poor prognosis, we examine the benefits of receiving transcranial magnetic stimulation treatment to improve his akinetic mutism.

Methods: We utilized independent component analysis with resting-state functional magnetic resonance imaging (rsfMRI) to better understand his cortical functionality. The imaging suggested absence of the default mode network (DMN). The patient underwent five sessions of navigated intermittent theta burst stimulation to the ipsilesional inferior parietal lobule and inferior frontal gyrus, with the aim of improving his default mode network functionality.

Results: No other treatments resulted in an improvement of this patient's condition; however, 3 weeks following transcranial magnetic stimulation treatment, the patient was more alert and interactive, and his follow-up rsfMRI scan demonstrated a partially intact default mode network.

Conclusion: This case raises important questions regarding the clinical utility of transcranial magnetic stimulation to improve the connectivity of important cerebral networks and subsequent related functional recovery.

Keywords: default mode network; glioblastoma; right frontal tumor; theta burst stimulation; transcranial magnetic stimulation; tumor resection.

FIGURE 1

(a) T2‐weighted axial and (b) T1‐weighted sagittal preoperative magnetic resonance imaging demonstrates a large, cystic glioblastoma in the right frontal lobe that extends medially to compress midline structures. White arrows highlight the position of the cystic component of the tumor in panels (a) and (b). (c) T1‐weighted axial and (d) T1‐weighted sagittal imaging demonstrates the extent of tumor resection following awake craniotomy

FIGURE 2

Resting‐state functional magnetic resonance imaging data demonstrating the independent component analysis (ICA) of the default mode network (DMN) in the patient (a) pretranscranial magnetic stimulation (TMS) and (b) post‐TMS. Blue arrows represent the posterior cingulate cortex, green arrows represent inferior parietal cortex, and yellow arrows represent the anterior cingulate cortex, wherein the DMN components would be expected to be seen. There was no clear evidence of the DMN in the pre‐TMS (a) ICA analysis as demonstrated by no components near the arrows. The closest component in the pre‐TMS (a) analysis near the posterior cingulate cortex seems to represent the default attention network, not the DMN. Post‐TMS (b), components representing the DMN appeared, as seen by the red areas of activity demonstrated by the arrows