A primary function of the glossopharyngeal (9th cranial) and vagus (10th cranial) nerves is to carry sensation from a number of structures around the back of the throat to the brainstem. Abnormal functioning of these nerves in glossopharyngeal neuralgia (GPN) patients, however, results in severe bouts of shock-like pain within the nerves’ sensory distributions. Although patients with GPN may not appear sick to others, they suffer greatly.
The diagnosis of glossopharyngeal neuralgia is primarily clinical, meaning that it is based on a patient’s history and symptoms. Patients with GPN typically experience pain that is lancinating or “stabbing.” The pain is usually restricted to one side of the back of the throat and the rear portion of the tongue but some patients may experience sharp pain deep within the ear. While the episodes of pain may occur hundreds of times per day, there are discrete pain free intervals between attacks. Patients often report that the pain can be triggered in a characteristic way such as by drinking cold liquids. Finally, patients with GPN generally report pain relief after taking the drug carbamazepine, although this effect may diminish over the course of the disease.
There is no specific test for GPN. However, any patient presenting with the symptoms of this condition should undergo a number of diagnostic tests in order to rule out alternative causes of the symptoms. Magnetic resonance imaging of the brain and brainstem is performed with the use of a contrast agent in order to rule out less common causes of glossopharyngeal pain such as multiple sclerosis, tumor, or vascular malformation. Additionally, during the preoperative workup, some patients may need a consultation with specialists in either otolaryngology or gastroenterology in order to rule out alternative explanations for the pain. Glossopharyngeal pain caused by confounding diagnoses requires treatment of the primary disorder.
In the majority of patients experiencing symptoms of GPN, however, the cause is an artery compressing the glossopharyngeal nerve near its point of emergence from the brainstem. Our center has been instrumental in pioneering the use of preoperative imaging in order to predict detect neurovascular compression in advance of the actual surgical exploration. This technique is important because it can save a patient without a clear neurovascular conflict from undergoing what would be a futile operation. Therefore, all patients evaluated with GPN undergo a specially protocolled MRI scan in order to detect treatable neurovascular compression.
The first-line treatment of GPN is medical therapy. Because opioids and non-steroidal anti-inflammatory medications are ineffective against neuropathic pain, anticonvulsant medications are employed. The most commonly effective drug is carbamazepine (Tegretol) but other choices may include gabapentin (Neurontin), phenytoin (Dilantin), pregabalin (Lyrica), oxcarbazepine (Trileptal), and baclofen (Lioresal).
While some patients may find that medical therapy brings their symptoms under satisfactory control, many patients find that their pain either becomes refractory to medication or requires increasing medication doses, over time. Eventually the side effects of medication, such as lethargy, may become intolerable.
GPN patients who find medication no longer effective or tolerable may elect to undergo an operation known as microvascular decompression of the 9th and 10th cranial nerves. The operation is performed through a small incision behind the ear, which is typically hidden within the hairline. At UPMC, the operation is performed in a minimally invasive fashion through an opening approximately the size of a quarter. After the operation, patients are cared for on a regular nursing floor, encouraged to get out of bed and walk just hours after surgery, eat and drink normally, and are discharged home of the first or second postoperative day.
The operation carries a small risk of swallowing difficulty (< 5%), one-sided hearing loss (< 2%), stroke (< 1%), imbalance (< 1%), pain in the area of the incision (< 1%), and cerebrospinal fluid leak or infection (<1%).