By Elie Mrad
Article Topic: Glossopharyngeal Neuralgia
Authors: Elie Mourad, Miriam Hajj, Rita Kfoury
Editors: Odette El Ghawi, Joseph Akiki
Reviewer: Ethar Hazaimeh
Keywords: Cranial Nerves, Glossopharyngeal nerve disease, Idiopathic Neuralgia, Nerve Compression syndromes, Microvascular Decompression
Abstract
Glossopharyngeal neuralgia (GPN) is a rare condition characterized by severe, sharp pain in the areas supplied by the glossopharyngeal nerve (CN IX), such as the angle of the jaw, ear, tonsillar fossa, and the base of the tongue. It is often triggered by actions like chewing, swallowing, yawning, or drinking cold beverages. GPN’s causes are frequently idiopathic, but they can be associated with vascular compression, an elongated styloid process (Eagle syndrome), tumors, or demyelinating diseases. The nerve damage and abnormal signaling involved in GPN may be exacerbated by ephaptic conduction. Complications include autonomic effects like bradycardia, hypotension, and seizures, along with difficulties in swallowing and speaking. Diagnosis typically involves patient history, physical examination, and imaging studies such as MRI, MRA, and CT scans to rule out other conditions and identify possible structural abnormalities. Treatment options include medications, nerve blocks, and surgical interventions like microvascular decompression (MVD) or rhizotomy. While many patients achieve significant pain relief with treatment, some may experience recurring symptoms, with persistent cases often requiring surgical intervention. Due to its rarity and similarity with trigeminal neuralgia, diagnosing GPN can be particularly challenging and often requires detailed differential diagnosis. This article provides an in-depth review of GPN’s etiology, pathogenesis, clinical presentation, diagnosis, and treatment options, emphasizing a multidisciplinary approach to care.
Introduction
Glossopharyngeal neuralgia (GPN) is a rare disorder characterized by severe, sharp, and stabbing pain in the sensory distribution of the ninth cranial nerve, also known as the glossopharyngeal nerve. According to the International Classification of Headache Disorders, 3rd edition (ICHD-3), GPN is marked by brief, episodic, and unilateral pain with sudden onset and rapid cessation. The pain typically affects areas supplied by the glossopharyngeal nerve, including the angle of the jaw, ear, tonsillar fossa, and the base of the tongue, and may also involve branches of the tenth cranial nerve (CN X), which are responsible for the pharynx and ear. Pain episodes usually alternate between relief and recurrence, with each episode lasting from 2 seconds to 2 minutes and occurring up to 200 times daily [2].
The condition predominantly affects people over 50, with the risk increasing with age. Although head and neck pain is more common in women, glossopharyngeal neuralgia affects both men and women equally [3].
Etiology and pathogenesis
Understanding the pathogenesis of glossopharyngeal neuralgia (GPN) involves examining the anatomy and function of the glossopharyngeal nerve. This nerve, which originates from the lateral aspect of the pons between the inferior olive and the inferior cerebellar peduncle, has both sensory and motor functions. It provides sensory input from the posterior two-thirds of the tongue, the middle ear, and the pharynx, and receives visceral sensory input from the carotid body. Additionally, parasympathetic fibers from the inferior salivatory nucleus in the pons travel via the glossopharyngeal nerve before joining the lesser petrosal nerve, while motor fibers from the nucleus ambiguous in the medulla innervate the stylopharyngeal muscle [5].
Figure 1 illustrates the anatomical distribution and innervation of the glossopharyngeal nerve, highlighting its sensory branches and the regions affected in cases of glossopharyngeal neuralgia [6].
Figure 1: Anatomical distribution and innervation of the glossopharyngeal nerve
GPN primarily affects the sensory fibers of the glossopharyngeal nerve, including those from the oropharynx, mastoid, middle ear, Eustachian tube, and posterior third of the tongue. It also involves fibers responsible for taste and sensory input from the carotid body and sinus [2]. Consequently, patients may experience associated cardiovascular or neurological symptoms, such as asystole, bradycardia, hypotension, syncope, seizures, or even cardiac arrest, due to disruptions in parasympathetic nerve function [3].
The exact cause of GPN is often idiopathic, with potential contributing factors including nerve demyelination and degeneration of the glossopharyngeal and vagal nerves. However, GPN can also arise from anatomical and structural abnormalities. Specifically, compression of the glossopharyngeal nerve by an abnormally positioned artery, such as the posterior inferior cerebellar artery (PICA) at the nerve’s root entry zone, can lead to symptoms. This vascular compression may damage the nerve’s myelin sheath, leading to ephaptic conduction and abnormal nerve signaling, which increases neural excitability. Although it is not fully understood if vascular compression directly impacts structures within the nucleus associated with the glossopharyngeal nerve, disruption of myelination and subsequent ephaptic conduction are plausible explanations for the condition [5].
In addition, an unusually long styloid process, a bone at the base of the skull, can exert pressure on the nerve, as seen in Eagle syndrome. Rarely, GPN may also be associated with tumors in the brain or neck, abscesses, carotid artery aneurysms, or multiple sclerosis [4].
Clinical Presentation
The pain associated with glossopharyngeal neuralgia (GPN) is typically described as sharp, stabbing, shooting, or shocking. In some cases, patients may also describe the pain as burning or aching [8]. These intense pain episodes can be brief, lasting from a few seconds up to two minutes, but they can recur multiple times throughout the day. The severity of these episodes can be so intense that they may wake a person from sleep. The pain can persist for weeks or months, with periods of remission occurring in between [9].
Pain in GPN primarily affects specific areas that are innervated by the glossopharyngeal nerve. One of the main locations affected is the back of the nose and throat, known as the nasopharynx. The pain can also be localized to the back of the tongue, radiating towards the ear, or even originating from it. Additionally, discomfort may be felt in the throat, and around the tonsils, and in some cases, it may extend to the voice box (larynx) [7, 10]. In some cases, the pain may spread from the initial site to other areas, such as the jaw, ipsilateral ear, shoulder, or back. This radiating pain can vary in intensity and may move between different locations [4], [9].
Pain episodes in GPN can be triggered by a variety of common actions. Chewing, coughing, laughing, speaking, and swallowing are frequent triggers that can provoke sudden pain. Yawning, sneezing, and drinking cold beverages are also known to initiate pain episodes. In some cases, even touching the affected tonsil with a blunt object can trigger the pain [7, 8]. These triggers make the condition particularly challenging, as they can interfere with routine activities and significantly impact the patient’s quality of life.
Complications
Autonomic Effects
Glossopharyngeal neuralgia (GPN) can lead to significant complications due to its proximity to the Vagus nerve, which is involved in autonomic nervous system functions. One serious complication is bradycardia, a condition where the heart rate slows significantly, which can be life-threatening. This occurs because damage to the glossopharyngeal nerve may result in excessive parasympathetic activation [4, 8, 9]. Additionally, GPN can cause fainting or syncope due to sudden drops in blood pressure or heart rate [4, 9]. Irregular heart rhythms and arrhythmias, are other potential issues, impacting overall cardiovascular health [8, 9]. In severe cases, GPN can trigger seizures, which are due to uncontrolled electrical activity in the brain [4, 9].
Physical Impact
The severe pain associated with glossopharyngeal neuralgia (GPN) can significantly impair an individual’s ability to swallow food and speak, making these basic functions extremely challenging [7, 10, 11]. This difficulty with swallowing and speaking often leads to unintended weight loss, as the discomfort experienced during eating may cause individuals to reduce their food intake [12].
Medication Side Effects
The medications used to manage GPN may have side effects, which can complicate the treatment process and affect the overall well-being of the patient [7, 10].
Trauma-Related Complications
In rare cases, injuries such as stab wounds can damage the carotid or internal jugular arteries, which may be associated with GPN [7, 11].
Workup and Diagnosis
To diagnose glossopharyngeal neuralgia (GPN), clinicians rely on patient-reported symptoms, which are then clinically evaluated through a comprehensive examination and diagnostic testing to confirm the diagnosis.
Clinical Evaluation
Initial diagnosis begins with a comprehensive history and physical examination. A common diagnostic maneuver involves touching the back of the throat with a cotton swab. For patients with GPN, this often triggers pain. In reality, the application of a local anesthetic to the same area can help confirm the diagnosis if pain relief is achieved during anesthesia [8, 11].
Imaging Studies
Magnetic Resonance Imaging (MRI) is essential for visualizing the glossopharyngeal nerve and detecting structural abnormalities such as vascular compression or tumors. An MRI with contrast is particularly effective for highlighting abnormal enhancements of the nerve or surrounding tissues, with thin-section T2-weighted images being preferred for assessing nerve compression and related pathologies [1]. Magnetic Resonance Angiography (MRA) complements this by evaluating the presence of vascular loops or compressions affecting CN IX root entry zone, thus helping to identify vascular causes resulting in GPN. [1, 9].
Computed Tomography (CT) scans are useful for identifying structural abnormalities, such as an elongated or ossified styloid process that may compress the glossopharyngeal nerve. While CT does not directly visualize the nerve, it provides valuable insights into surrounding anatomical structures [1, 9].
X-rays, although less detailed compared to CT or MRI, can reveal an elongated or heavily calcified styloid process in the cervical spine, which may contribute to nerve compression, offering additional diagnostic information [1].
Additional Testing
Basic laboratory tests, including a complete blood count (CBC), basic metabolic panel, erythrocyte sedimentation rate (ESR), and anti-nuclear antibodies (ANA), are conducted to rule out infections, inflammation, malignancies, or temporal arteritis.
Persistent or unusual symptoms may require further evaluations, such as a cardiology assessment with echocardiogram and Holter monitoring, especially if syncope or other cardiac issues are suspected as complications discussed earlier in this article [1].
To conclude, diagnosing glossopharyngeal neuralgia involves a multifaceted approach, combining detailed clinical evaluation with various imaging modalities. Accurate diagnosis requires distinguishing GPN from other similar conditions and may necessitate specialist consultation and additional testing to ensure effective management and treatment.
Differential Diagnosis
Accurate diagnosis of GPN involves differentiating it from several other conditions with overlapping symptoms:
Glossopharyngeal neuralgia (GPN) and trigeminal neuralgia are both types of cranial neuralgias with similar underlying mechanisms, but they differ significantly in their presentation. GPN typically presents with pain localized to the throat and tonsillar region, which is aggravated by swallowing and chewing. In contrast, trigeminal neuralgia affects the facial area, with pain often triggered by light touch or activities such as washing the face or brushing teeth. The rarity of GPN compared to trigeminal neuralgia can lead to it being underdiagnosed, making a thorough patient history and physical examination crucial for accurate diagnosis [1, 13].
Jacobson’s Neuralgia, also known as Intermedius Neuralgia, involves pain and sensory disturbances primarily in the ear, which can mimic the otic variant of glossopharyngeal neuralgia (GPN). However, Jacobson’s Neuralgia is distinct in that it presents exclusively with ear symptoms, while GPN affects the throat and tonsils [1, 13].
Temporal arteritis may present with pain similar to GPN but is typically accompanied by additional symptoms such as headaches and vision problems. These distinguishing features are crucial for differentiating temporal arteritis from GPN [13].
Temporomandibular Joint Dysfunction (TMD) can cause pain in areas overlapping with GPN symptoms but typically involves specific jaw movements and symptoms such as jaw clicking, which are not characteristic of GPN [13].
Treatment and Management
Treatment strategies encompass medications, interventional procedures, and various surgical options.
Medication Management
The cornerstone of treatment for glossopharyngeal neuralgia involves pharmacotherapy. The most effective medications are anti-seizure drugs, which help control nerve cell activity and alleviate pain. First-line medications for managing glossopharyngeal neuralgia include carbamazepine, which is often considered the primary treatment due to its effectiveness in stabilizing nerve cell activity and reducing pain [7, 8]. Additionally, gabapentin and oxcarbazepine, along with phenytoin, are frequently used either as alternative or adjunct treatments to carbamazepine [7, 9, 11].
In addition to anti-seizure medications, baclofen and tricyclic antidepressants such as amitriptyline may offer symptom relief, particularly if primary medications prove ineffective [8, 9]. For individuals who do not respond well to these treatments or experience significant side effects, other options such as pregabalin and lamotrigine might be considered [1].
Medication management usually begins with lower doses, which are gradually increased based on effectiveness and tolerability. It is crucial to monitor patients for potential side effects, which can include drowsiness, nausea, and skin rash. Regular blood tests are often required to ensure drug levels remain within safe ranges and to manage any adverse effects [1, 8].
Local and Nerve Block Procedures
When medications provide insufficient relief for glossopharyngeal neuralgia, local and nerve block procedures can offer valuable alternatives. Local anesthetics, such as lidocaine or xylocaine, can provide temporary pain relief by being applied to the affected area of the throat. This method is particularly useful for managing pain during activities like eating and speaking [8, 9]. Additionally, nerve blocks involve injecting a local anesthetic around the affected nerve to disrupt pain transmission, offering both diagnostic and therapeutic benefits [1, 4]. This targeted approach can significantly alleviate symptoms in cases where other treatments have been inadequate.
Surgical Interventions
When conservative treatments fail to provide sufficient relief for glossopharyngeal neuralgia, surgical options may be necessary to address the underlying cause of the condition. One common surgical intervention is Microvascular Decompression (MVD), which is performed when a blood vessel compresses the glossopharyngeal nerve. During this procedure, a small incision is made in the skull, and a Teflon pad is placed between the nerve and the blood vessel to relieve the pressure. MVD is effective, with a high success rate of 80-85% in providing pain relief [1, 8, 12]. The procedure is generally safe, though advanced age does not impact outcomes adversely; however, obesity and diabetes may increase the risk of reoperation and warrant extra caution [14]. MVD may also be utilized in the context of Combined Hyperactive Dysfunction Syndrome (HDS), a rare condition involving symptoms from cranial nerve overactivity, including trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia, without a clear structural lesion [15].
If MVD is not feasible or effective, the surgeon might consider rhizotomy. This procedure involves cutting specific nerve fibers responsible for transmitting pain signals, offering up to 96% long-term pain relief. However, it can lead to complications such as voice hoarseness or difficulties with swallowing [1, 8, 12]. Adding rhizotomy of cranial nerve X may improve long-term pain control but also increases the risk of permanent dysphagia and vocal cord paralysis, making it essential to weigh the benefits against these significant risks [16].
Other surgical options include percutaneous radiofrequency rhizotomy, a minimally invasive procedure where a needle is inserted through the cheek to destroy nerve fibers with heat. This technique is often performed on an outpatient basis [8].
Additional Supportive Treatments
Beyond primary treatment modalities for glossopharyngeal neuralgia, several supportive measures can offer additional benefits. Applying cold or hot compresses to the affected areas may provide temporary relief from pain. In addition, physical therapy and psychological counseling can be valuable adjunctive therapies. While the effectiveness of these interventions may vary, they can contribute positively to managing symptoms and enhancing overall quality of life when used alongside other treatments [1].
In summary, the management of glossopharyngeal neuralgia involves a multi-faceted approach. Medications, particularly antiseizure drugs, are the first-line treatment, with additional options available if initial treatments fail. Local anesthetics and nerve blocks provide temporary relief, while surgical options, including microvascular decompression and rhizotomy, offer significant potential for long-term pain relief. Each patient’s treatment plan should be customized based on their specific symptoms, response to therapy, and overall health.
Prevention
Glossopharyngeal neuralgia typically occurs unexpectedly, and in most cases, healthcare providers are unable to identify a cause or reason for it. As a result, prevention is not possible, and no guaranteed method exists to reduce the risk of developing the condition [8].
Risk factors
GPN, similar to trigeminal neuralgia, typically occurs in individuals aged 50 and older. The likelihood of developing GPN increases with age, making age the primary risk factor [4]. Although women generally experience more pain in the head and neck regions and exhibit a higher incidence of orofacial pain, GPN does not appear to favor one gender over the other. Consequently, both men and women are equally affected by GPN [17].
GPN can also be a temporary or permanent postoperative complication, particularly following surgeries involving the head, neck, or base of the skull, due to glossopharyngeal nerve injury. Such procedures include reconstructive surgery of the carotid arteries [18], carotid endarterectomy [19, 20], and even open-heart surgery. The latter is associated with the duration of the surgery, pressure from the endotracheal tube cuff, the transesophageal echocardiography probe, and the positioning of the head and neck [21].
Prognosis
Glossopharyngeal neuralgia (GPN) is typically a temporary condition, lasting for weeks or months. Most individuals experience it only once in their lifetime. However, some people may experience recurring phases of GPN symptoms, with episodes lasting for weeks or months followed by periods of remission. This cycle can repeat over several years [9].
GPN generally does not affect life expectancy, and the prognosis is usually favorable, with many individuals eventually seeing their symptoms disappear. The outlook can be less favorable for those with severe symptoms, especially if they experience pain on both sides of the head, constant pain, or exceptionally intense pain. Additionally, symptoms such as fainting and changes in heart rhythm can increase the risk of a negative outcome [9].
While GPN often resolves on its own, treatment can significantly improve outcomes. Effective treatment options are available, and surgical interventions can provide either temporary or long-lasting pain relief [9]. A study evaluating long-term outcomes following surgical treatment found that 90% of patients experienced complete pain relief immediately after surgery, with the remaining patients reporting improvement. The study noted no deaths, with 20% of patients experiencing short-term complications that resolved, although 10% had persistent hoarseness. At a follow-up with an average duration of 4 years, there were no recurrences of symptoms, demonstrating that surgery is both safe and effective for treating Vago-glossopharyngeal neuralgia [22].
However, a reported incidence of 30.84% high-frequency hearing loss (HFHL) following microvascular decompression (MVD) for trigeminal neuralgia (TGN), glossopharyngeal neuralgia (GPN), or geniculate neuralgia (GN) highlights a potential complication, with the highest incidence occurring on the ipsilateral side [23].
Recent updates
In recent years, several novel treatment options for glossopharyngeal neuralgia (GPN) have gained recognition and popularity. Stereotactic radiosurgery (SRS) has emerged as an alternative treatment approach, utilizing nerve ablation to relieve symptoms. Compared to traditional methods like microvascular decompression (MVD) and rhizotomy, SRS has shown promising short-term pain reduction, especially with radiation doses of 75 Gy or more. However, its long-term effectiveness in maintaining pain relief has been somewhat lower. Despite that, SRS remains a safe and effective option for GPN, providing favorable pain relief and low complication rates [24, 25].
Another innovative approach is fully endoscopic microvascular decompression (E-MVD), which addresses neurovascular compression (NVC) conditions such as GPN. E-MVD offers several advantages over traditional microscopic MVD, including reduced risk of surgical complications, enhanced treatment effectiveness, and potentially lower likelihood of recurrence [26].
Ultrasound-guided glossopharyngeal nerve blocks (UGPNB) have also gained traction as an effective, safe, and minimally invasive treatment option. This method allows for repeatable and targeted pain relief, making it a valuable alternative or adjunct to more invasive procedures. UGPNB might be considered before opting for intracranial surgery or neurodestructive interventions [27].
Additionally, radiofrequency ablation (RFA) has demonstrated effectiveness in treating GPN, with more than 80% of patients reporting pain relief following the procedure. Nonetheless, further clinical and controlled trials are needed to better understand the long-term outcomes of RFA for GPN patients. [28].
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