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INTRODUCTION
Glossopharyngeal neuralgia (GPN) is a rare condition, occurring with a frequency of about 1% of that of trigeminal neuralgia6,7). Its reported incidence is approximately 0.8 per 100000 people. Vascular compression is a common and treatable cause.
The cerebellopontine angle (CPA) lipomas causing trigeminal neuralgia or hemifacial spasm are uncommon and a lipoma causing GPN is extremely rare. Because of the rare occurrence of these tumors of the CPA lipoma causing GPN, the experience in the therapeutic management is limited.
We report a rare case of GPN caused by a lipoma with a review of the literature.
CASE REPORT
A 46-year-old woman complained of 2-year history of severe right throat pain, and ipsilateral otalgic pain. The throat pain was described as an episodic lancinating character confined to the right side. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed a suspicious offending posterior inferior cerebellar artery (PICA) compressing lower cranial nerves including glossopharyngeal nerve (Fig. 1).
Preoperatively, an electromyogram-motor nerve conduction velocity [EMG-MCV, Medelec Synergy (EMG/EP), YoungWoo-Meditec, Seoul, Korea] of facial nerve, and otolaryngologic evaluation were carried.
To detect vascular anatomy causing a neuralgic pain and to inspect relationships between offending vessels and causative nerve, MRI, magnetic resonance angiography (MRA) and computed tomographic angiography (CTA, Philips Biliance, Cleveland, OH, USA) were studied. MRI was performed on 1.5 T (Sigma EXCI-TE, General Electronics, Milwaukee, WI, USA) or 3.0-T scanners (Achieva, Philips, Eindhoven, The Netherland).
A retromastoid lateral suboccipital craniotomy was performed to visualize the root entry zone of glossopharyngeal, vagus and accessory nerves. A soft, yellowish mass (2×3×3 mm in size) was found incorporating the lateral aspect of proximal portion of 9th and 10th cranial nerves. Therefore, the proximal portion of 9th nerve was displaced medially. The distal portion of glossopharyngeal nerve was pushed laterally by pulsatory compression of PICA (Fig. 2). Microvascular decompression (MVD) of the offending PICA was performed. No additional procedure to remove the lipoma was carried out. Immediate postoperatively, her severe lancinating pain remained unchanged. However, the neuralgic pain intensity diminished gradually over a period of several weeks and disappeared. One year later, her pain developed intermittently, however its intensity is tolerable and well controlled with intermittent carbamazepine.
DISCUSSION
GPN is characterized by severe, unilateral lancinating and paroxysmal pain on tongue base, throat, and tonsil, triggered by swallowing, chewing, coughing, yawning, etc4,11,12). Treatment modalities for GPN include medications8), Gamma knife radiosurgery13,16), or MVD6,7). MVD of the GPN via lateral suboccipital infrafloccular approach is a good curative treatment modality for GPN7,10), despite its known low operative success rate.
Although lipomas are the most common form of soft tissue neoplasm, its intracranial form is exceedingly rare and most of them are found incidentally during neuroradiological study15) with an incidence of 0.08%, accounting for only 0.1% of all CPA masses14). A few papers were published regarding lipoma causing cranial rhizopathy1,2,3,15,17), including trigeminal neuralgia1) and hemifacial spasm2,3). By 1995, only up to 46 cases of CPA lipoma had been reported in the literature with 7 cases causative of trigeminal neuralgia17). The mechanism can be attributed to 5th nerve pushing against the blood vessel rather than the usual arterial cross-compression1). It was suggested that minimal excision of the lipoma or a partial rhizotomy was enough to relieve trigeminal neuralgia symptoms5).
The CPA lipomas tend to envelop cranial nerves and have attachments to the brain stem that treatment of these tumors should be conservative. Furthermore, as CPA lipoma resection is associated with a high risk of neurologic morbidity and lesion progression is unusual, conservative observation remain the default strategy in most patients9,15). And, limited surgery is indicated if the patients suffer from disabling neurological symptoms and signs1,3).
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