Resection of intrinsic tumors from nondominant face motor cortex using stimulation mapping: Report of two cases

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Resection of Intrinsic Tumors from Nondominant Face Motor Cortex Using Stimulation Mapping: Report of Two Cases P. D. LeRoux, M .D., M . S . Berger, M.D., M. M . Haglund, M .D ., W. H . Pilcher, M .D., and G. A . Ojemann, M .D . Department of Neurological Surgery, University of Washington Medical Center, Seattle, Washington

LeRoux PD, Berger MS, Haglund MM, Pilcher WH, Ojemann GA . Resection of intrinsic rumors from nondominant face motor cortex using stimulation mapping : report of two cases. Surg Neurol 1991 ;36 :44-8 .

We report two right-handed patients who underwent resection of intrinsic glial tumors from the nondominant hemisphere, face motor cortex. Both patients underwent preoperative assessment with computed tomography and magnetic resonance imaging localizing the tumor in the inferior region of the Rolandic cortex . With the patients under general anesthesia and without muscular paralysis, the tumor volume was determined by intraoperative ultrasound and resective surgery accomplished with the aid of cortical and subcortical stimulation mapping techniques . Radical resection of the tumor from the face motor cortex was achieved in both patients . A transient contralateral facial weakness and apraxia were noted in each patient, and this resolved within 6 to 8 weeks following surgery . Removal of intrinsic tumors involving the nondominant face motor cortex may be safely achieved using brain mapping techniques to localize inferior Rolandic cortex and avoid resection of the hand motor cortex and descending subcortical motor pathways . Permanent disability will be prevented due to the bilateral representation of face motor function at the neocortical level . However, due to language localization in cortical zones contiguous with the dominant hemisphere, face motor cortex, we do not recommend resection of this region . KEY WORDS :

Brain mapping ; Brain tumor ; Cortical resection ;

Motor cortex

Recent reports have suggested that an aggressive approach toward the resection of intrinsic brain tumors results in an improved quality of life and prolonged survival [1,8,14,22] . This approach, however, is often limited by functionally eloquent areas within or adjacent

Address reprint requests to : M . S . Berger, M .D., Department of Neurological Surgery, RI-20, University of Washington Medical Cenrer, 1959 NE Pacific, Seattle, Washington 19891 . Received October 4, 1990 ; accepted December 19, 1990 . 6.

1991

by Elsevier Science Publishing

Co., Inc.

to the tumor nidus . Brain mapping techniques using either somatosensory evoked potentials or direct cortical stimulation have been adapted for use in neurosurgical oncology to identify these important regions, thus maximizing the extent of resection while minimizing operative morbidity [5-7,13,34] . In this report, we describe the results using cortical and subcortical stimulation mapping to allow for resection of intrinsic tumors within the nondominant hemisphere, face motor cortex . Following a transient contralateral facial paresis and apraxia, full recovery of function is expected due to the bilateral cortical representation of facial muscle movements [4,11,16,19,24,29,341 .

Materials and Methods Two patients were identified from our neurooncology brain mapping files who had clinical and diagnostic imaging evidence of an intrinsic tumor primarily occupying the inferior Rolandic (orofacial) cortex of the nondominant (right) cerebral hemisphere . Both patients were strongly right handed for all motor skills, therefore a WADA test for speech localization was not performed . Postoperatively, neither patient had language dysfunction, which should have developed following tumor resection due to the known proximity of Broca's area to the face motor cortex of the dominant hemisphere . Therefore, the tumor in both patients was felt to be located within the nondominant (right) cerebral hemisphere . Surgery was performed with the patients under general anesthesia and without muscular paralysis until motor mapping was complete . Stimulation mapping techniques for localization of the motor cortex have been previously outlined [6] . Briefly, a bipolar electrode with 5 mm of spacing between the tips is applied to the brain surface for 2 to 3 seconds . A biphasic, square-wave pulse (60 Hz, 1-ms duration) is delivered from a constant current generator to the brain surface to elicit the desired orofacial and hand motor responses . The current will vary between 2 and 16 mA, depending upon the anesthetic conditions of the patient. During tumor removal, 0090-3019/91/$3 .50



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Face Motor Cortex Tumor Resection

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ments using a current of 6 to 8 mA (Figure 2) . Tumor resection was guided by IOUS and subcortical stimulation resulting in a near total resection (95 %) . The inferior part of the motor cortex was resected up to the hand motor region, which was not removed . Postoperatively, the patient had weakness of the left lower face, which resolved within 6 weeks following surgery .

Case 2

Figure 1 . Ti-weighted sagittal MRI depicting the tumor involving the perirylvian region on the right side (arrow) ,

subcortical stimulation was respectively carried out to localize the descending motor pathways .

A 54-year-old, right-handed man presented with a 4-month history of episodic paresthesias involving left face and ipsilateral hand clumsiness . The patient also had evidence of mild apraxia involving the left lower face . An MRI revealed a nongadolinium-enhancing lesion involving the inferior aspect of the Rolandic cortex (Figure 3) . A right frontotemporal craniotomy was performed and the tumor was localized and delineated using bOUS . Stimulation mapping at 6 mA resulted in jaw and left orofacial movements (Figure 4) . At the superior edge of the tumor, left wrist flexion was elicited . The entire face motor cortex was resected up to the hand region, resulting in a gross total removal of the tumor (Figure 5) . The resection was guided by subcortical mapping, which identified underlying motor tracts emanating from the hand motor cortex . Postoperatively, the patient had weakness of the left hand and an ipsilateral facial droop, which resolved within 6 to 8 weeks following surgery . No sensory deficits of the face or hand were identified .

Case Reports Case I

An 18-year-old, right-handed man presented to the Neuro-Oncology Service with intermittent numbness involving the left face and upper extremity and a mild facial droop on the same side . The patient had previously undergone a subtotal resection, followed by radiation therapy, for a right temporal-parietal pleomorphic xanthoastrocytoma at 7 years of age . Magnetic resonance imaging (MRI) demonstrated a right perisylvian tumor of mixed signal intensity withoutgadolinium enhancement . The lesion involved the right superior temporal gyrus and extended superiorly into the inferior frontoparietal region (Figure 1) . A right frontotemporal craniotomy was performed with the patient under general anesthesia and without muscular paralysis . Intraoperative ultrasound (IOUS) confirmed tumor involvement of the superior temporal gyrus and the inferior surface of the frontoparietal junction . Stimulation mapping resulted in pharyngeal contractions and left orofacial and upper extremity move-

Figure

2 . Schematic drawing of exposed surgical field ._A through H represent the underlying echogenic abnormalities depicted by ultrasound M is the motor cortex involving the left hand and FM is the beginning of the face motor, rtex and ascends rostrally toward the hand area . The shaded areas depict extent of tumor resection .



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LeRoux et at

Figure

5 . Postresection brain map . Tumor removal ends at beginning of the hand motor cortex (dared trian le) . Descending subcortical motor fibers from the hand region were ientifted during stimulation mapping (white arrows) ,

Figure

3 . TI-weighted corona! MRI demonstrating suprasylcian tumor involving inferior Rolandic cortex (arrows) .

Discussion Advances in adjuvant forms of therapy for glial neoplasms have renewed the interest in first achieving a maximal tumor resection while maintaining or improving the patient's functional status [1,8,14,22] . This goal

Figure

4 . Presection brain map showing face motor cortex (open arrows) expanded with tumor . The hand area of the motor cortex is normal in appearance (solid arrow) .

has been difficult to accomplish when the tumor is present within or adjacent to eloquent brain regions, such as the Rolandic and speech cortex . Resective surgery for intrinsic lesions using intraoperative stimulation mapping techniques has been recently advocated as a useful technique to identify critical functional areas during tumor removal [5-7,13,18} . The stimulation mapping technique is not a new concept, especially as it has been applied to language and motor localization during epilepsy surgery [25-31] . Direct cortical stimulation of the Rolandic region to elicit contralateral movements dates back to Bartholow [2] and Cushing [9] . However, until recently described by Berger et al [5,6], subcortical localization of descending motor pathways during tumor removal has not been used to facilitate the resection . Removal of cortical zones responsible for stimulationinduced contralateral movements will result in loss of function, although some recovery may subsequently occur 110,11,29,31,32] . However, this concept does not apply to the face motor cortex, which may be resected without permanent facial weakness [12] . The anatomic organization in the Rolandic cortex of orofacial muscles is functionally different from that of the limb muscles such that bilateral coordination of facial movements is often required [23] . Conventional teaching based on cortical disease due to stroke and injury has emphasized the bilateral innervation of the upper facial muscles and contralateral innervation of the lower facial muscles . Studies in primates and humans 1 16,19,201 suggest that corticofacial projections are at variance with the traditional concepts . The facial nucleus in the pons is divided into a dorsal section, supplying upper facial muscles, and a lateral segment, projecting to lower facial muscles .



Face Motor Cortex Tumor Resection

Dorsal facial nuclei receive scant cortical innervation and rely more on projections from nearby neurons in the pontine reticular formation, while lower facial nuclei receive bilateral cortical innervation with contralateral predominance . Additional experimental work in primates with cortical microstimulation has revealed both bilateral and ipsilateral somatosensory afferent input to the face motor cortex, which is very rarely found within the primary limb motor cortex . Transcranial magnetic stimulation in normal human volunteers has verified bilateral cortical influence on facial muscles [4] . When patients with lesions involving the inferior Rolandic cortex were evaluated, stimulation over the affected hemisphere failed to produce any responses in the facial muscles, whereas stimulation over the uninvolved hemisphere produced responses in both normal and paretic muscles . Ipsilateral and bilateral responses in the tongue, jaw, pharynx, and facial muscles have been described following cortical stimulation in humans and primates [3,11,15,21,24,29,31-33] . These responses are not abolished with callosal sectioning [111 . However, we are not aware of examples in the literature with ipsilateral or bilateral limb responses following cortical stimulation in humans [11,29,311 . In our two cases, we did nor find ipsilateral or bilateral facial responses in either patient who had documented stimulation-induced contralateral orofacial movements . Following resection of the functional face cortex infiltrated with tumor, both patients developed transient weakness of the lower, more than the upper, facial muscles, with eventual full recovery being restored . Although there is individual variability in the location of speech cortex [28], it is closely related anatomically and functionally to the inferior Rolandic cortex of the dominant hemisphere [17,25,26] . Therefore, we would not advocate resection of the face motor cortex in the dominant hemisphere . Added safety may be gained during resection of the nondominant face motor region with the addition of subcortical stimulation mapping at the superior margin to prevent injury to the descending motor tracts originating from the hand motor cortex . This work was supported by an American Cancer Society Career Development Award and a Clinical Investigator's Development Award NS 01253-01, and by National Institutes of Health Grants NS I-11 I, 21724 . and 20482 .

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