The hypoglossal nerve (CN XII) may be placed at risk during posterior fossa surgeries. The use of intraoperative monitoring (IOM), including the utilization of spontaneous and triggered electromyography (EMG), from tongue muscles innervated by CN XII has been used to reduce these risks. However, there were few reports regarding the intraoperative transcranial motor evoked potential (MEP) of hypoglossal nerve from the tongue muscles. For this reason, we report here two cases of intraoperative hypoglossal MEP monitoring in brain surgery as an indicator of hypoglossal deficits. Although the amplitude of the MEP was reduced in both patients, only in the case 1 whose MEP was disappeared demonstrated the neurological deficits of the hypoglossal nerve. Therefore, the disappearance of the hypoglossal MEP recorded from the tongue, could be considered a predictor of the postoperative hypoglossal nerve deficits.
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Collet-Sicard syndrome is a rare syndrome that involves paralysis of 9th to 12th cranial nerves. We report an uncommon case of schwannoma of the hypoglossal nerve in a 39-year-old woman presented with slurred speech, hoarse voice, and swallowing difficulty. Physical examination revealed decreased gag reflex on the right side, decreased laryngeal elevation, tongue deviation to the right side, and weakness of right trapezius muscle. MRI revealed a mass lesion in the right parapharyngeal space below the jugular foramen. The tumor was surgically removed. It was confirmed as hypoglossal nerve schwannoma via pathologic examination. Videofluoroscopic swallowing study revealed aspiration of liquid food and severe bolus retention in the vallecula and piriform sinus. Laryngoscopy revealed right vocal cord palsy. Electrodiagnostic study revealed paralysis of the right 11th cranial nerve. In summary, we report an uncommon case of schwannoma of the hypoglossal nerve with 9th to 12th cranial nerve palsy presenting as Collet-Sicard syndrome.
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Occipital condyle fractures (OCFs) with selective involvement of the hypoglossal canal are rare. OCFs usually occur after major trauma and combine multiple fractures. We describe a 38-year-old man who presented with neck pain and a tongue deviation to the right side after a traffic accident. Severe limitations were detected during active and passive range of neck motion in all directions. A physical examination revealed a normal gag reflex and normal mobility of the palate, larynx, and shoulder girdle. He had normal taste and general sensation in his tongue. However, he presented with a tongue deviation to the right side on protrusion. A videofluoroscopic swallowing study revealed piecemeal deglutition due to decreased tongue mobility but no aspiration of food. Plain X-ray film findings were negative, but a computed tomography study with coronal reconstruction demonstrated a right OCF involving the hypoglossal canal. An electrodiagnostic study revealed evidence of right hypoglossal nerve palsy. We report a rare case of isolated hypoglossal nerve palsy caused by an OCF.
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We examined 16 patients with unilateral tongue deviation using magnetic stimulator in order to evaluate central hypoglossal nerve palsy following brain injury.
Surface recording electrodes were placed at the apex and anterolateral one thirds of tongue. Magnetic stimulation was performed at vertex and occiput. On occiput stimulation, the mean latency was 3.77⁑0.36 msec in affected side and 3.89⁑0.47 msec in sound side for male patients, and 3.94⁑0.61 msec, 3.90⁑0.55 msec respectively for female patients. The mean amplitude was 0.85⁑0.63 mV in affected side and 2.64⁑2.32 mV in sound side for male patients and 1.00⁑0.23 mV, 3.56⁑0.40 mV respectively for female patients. There was significant difference between affected side and sound side for amplitude.
On vertex stimulation, the mean latency was 8.61⁑0.83 msec in affected side and 7.50⁑0.80 msec in sound side for male patients, and 9.66⁑1.14 msec, 6.48⁑0.44 msec respectively for female patients. The mean amplitude was 0.77⁑0.59 mV in affected side and 1.23⁑1.08 mV in sound side for male patients and 0.52⁑0.23 mV, 1.15⁑0.64 mV respectively for female patients. There was significant difference between affected side and sound side for latency and amplitude.
We examined 16 healthy adults in order to evaluate the hypoglossal nerve using magnetic stimulation. Surface electrodes were located in apex and anterolateral third of tongue. We stimulated two sites of head, vertex and occiput.
For occiput stimulation, the mean latency was 3.77±0.32 msec in male and 3.81±0.36 msec in female, for vertical stimulation, 6.94±0.56 msec, 6.91±0.52 msec respectively. For occiput stimulation, the mean amplitude was 4.84±2.80 mV in male and 5.09±2.88 mV in female, for vertical stimulation, 1.96±1.34 mV, 1.15±0.64 mV respectively.
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