An unusual anatomical explanation for contralateral upper extremity weakness after frontal craniotomy.

Contralateral upper extremity weakness following resection of a frontal tumor is not unusual to neurosurgeons. The differential diagnosis is broad and includes postoperative brachial plexopathy, which is usually secondary to malpositioning. We report the first known case of postoperative brachial plexopathy secondary to sialadenitis. A 53-year-old woman who had undergone an uncomplicated right frontal craniotomy for resection of a right frontal metastatic lesion developed left upper extremity weakness as well as extensive left neck edema immediately postoperatively. The edema, tracking along the fascial plane of the neck, caused compression of the upper (more superficial) elements of the brachial plexus and ensuing plexopathy. The cause of the neck edema was found to be sialadenitis of the submandibular gland. With medical treatment, the edema slowly resolved and the patient regained full function of her left upper extremity within weeks. This unusual case represents a new etiology of postoperative brachial plexopathy, illustrates the clinical relevance of the anatomy of the neck fasciae, and broadens the differential diagnosis of contralateral weakness following craniotomy for resection of a brain tumor.