Functional compensation of the claustrum: lessons from low-grade glioma surgery

Abstract

Keywords Claustrum AE Plasticity AE Low-grade glioma AEBrain mappingDespite many anatomical, histological and electro-physiological studies, essentially performed in animals,the function of the claustrum remains unclear [1]. Weknow only one lesional report in humans, which sug-gested, using somatosensory evoked potentials, thatthis structure might influence deeply the contralateralsomatosensory cortex [2]. Recently, PET studies inhealthy volunteers supported its involvement in moti-vational processes [3]. Moreover, because of a wide-spread connectivity of the claustrum, Crick and Kochproposed that this area could play a key role in con-sciousness [4]. Nevertheless, they also raised the fol-lowing question ‘‘What happens when the claustrum,or parts of it, have been transiently or permanentlyremoved? The answer to this important question is,unfortunately, not known’’ [5].Here, we report a series of 42 patients operated for acerebral glioma involving the claustrum, with func-tional recovery in all cases but three, despite a claustralremoval.We consecutively operated 42 right-handed patients(28 men, 14 women, mean age 36 years) harboring aparalimbic WHO grade II glioma developed primi-tively within the insula, and invading the claustrum.There was no previous medical history. The presentingsymptom was seizure in the 42 cases. Preoperatively, 40patients had a normal examination (2 mild dysphasias).The Mini Mental Status Examination (MMSE) was>27, and the Karnofsky Performance Status (KPS) >70in all cases. The Boston Diagnosis Aphasia Examina-tion (BDAE) was performed in the 12 patients har-boring a left tumor, with a normal score in 10 cases.All surgeries were conducted under intraoperativecortico-subcortical electrical mapping [6, 7]. A func-tional response was systematically induced by sub-cortical stimulation, leading to stop the resection inthe depth: motor response in the 30 patients operatedunder general anesthesia for a right tumor by stim-ulating the pyramidal pathways [8]; and languageresponse in the 12 patients operated whilst awake fora left tumor by stimulating the lateral part of thelentiform nucleus [9].Due to the absence of response before the stimula-tion of these deep eloquent structures, the claustrumwas removed in the 42 patients, as confirmed by controlMRI (Fig. 1). The glioma resection was total or sub-total in 31 patients, and partial in 11 patients due to theinvasion of structures which were still functional andthus surgically preserved—but not the claustrum.Postoperatively, 39 patients recovered a normalneurological examination within 3 months, withMMSE >27 and KPS >70. In addition, in the 12patients with a left tumor, BDAE score was normal,thus with an improvement in the 2 patients with apreoperative dysphasia. The 39 patients returned to anormal socio-professional life. Three patients experi-enced a permanent left hemiparesis because of a