The 12 Pairs of Cranial Nerves
Olfactory (smell)
Optic (vision)
Oculomotor (movement of eyes and focusing)
Trochlear (movement of eyes)
Trigeminal (sensation in the face, jaw muscles used in chewing)
Abducens (movement of eyes)
Facial (facial muscles, scalp, taste)
Acoustic or vestibulocochlear (hearing, balance)
Glossopharyngeal (taste, muscles used in swallowing, sensation in the pharynx and middle ear)
Vagal (movement and sensation in pharynx and larynx; sensation in abdominal organs; monitors heart rate, blood pressure, and digestion)
Accessory (muscles in pharynx, larynx, upper neck, and upper throat)
Hypoglossal (movement of tongue)
Glossopharyngeal neuralgia (GPN) is a somewhat rare condition characterized by severe, fierce episodes of pain localized to the external ear canal, the base of the tongue, the tonsil, or the area beneath the angle of the jaw. This pain is many times confused with Trigeminal Neuralgia and mistreated. It is related to hyperactivity of the glossopharyngeal nerve. GPN is rare compared with TN. The pain affects the sensory areas corresponding to the glossopharyngeal neuralgia with a branch of sensory vagus nerves. GPN consists of spasmodic, momentary, and severe sharp pain in the posterior area of the throat, tonsillar fossa, base of the tongue, ear canal, and areas inferior to the angle of the mandible. Generally, the pain persists for seconds to minutes and is often triggered by chewing, coughing, yawning, talking, and swallowing. Since Glossopharyngeal neuralgia is a relatively rare condition There are various diagnostic and management dilemmas.
Glossopharyngeal neuralgia is believed to be caused by irritation of the ninth cranial nerve, although in most cases, the source of irritation is never found.
Possible causes include:
neurovascular compression: blood vessels abutting the nerve root entry zone of the glossopharyngeal nerve
tumors at the base of the skull
tumors or infections of the throat and mouth
Radiographic features
The main role of imaging is to identify potential causes at the base of the skull.
CT
CT is unable to visualize the nerve but can delineate the pars nervosa of the jugular foramen.
MRI
MRI is the ideal way to image the nerve which can be seen particularly well on heavily T2 weighted thin section images (e.g. FIESTA/CISS). Contrast is also necessary to assess for abnormal enhancement of the nerve or surrounding structures.
Additionally, MRA is required to assess for a compressing vascular loop, most commonly found at the nerve root entry zone.
Historical Aspects
In 1910, Weisenburg first described GPN as a cause of Tic douloureux when a patient presented to him with lancinating pain of the throat and the ear. In 1921, Harris coined the term "glossopharyngeal neuralgia" describing it as a painful syndrome characterized by paroxysms of unilateral and severe lancinating pain in the distribution of the nerve, which may be aroused by stimulation of trigger points in regions of the nerve. The pain may be spontaneous or precipitated by a variety of actions that stimulate the region supplied by the glossopharyngeal nerve namely yawning, coughing, swallowing, and talking. In 1933, Reichert recognized the tympanic branch (Jacobson's Nerve) of glossopharyngeal nerve as a cause of ear pain in GPN. Wortis et al. (1942) first described GPN in association with cardiac arrest and syncope that are unusual presentations of GPN.
GPN is a mixture of cranial nerves that have somatic sensory fibers from the oropharynx, mastoid, middle ear, and Eustachian tube, and posterior third of the tongue. The middle ear and mastoid have a sensory supply of glossopharyngeal nerve along with the tympanic branch or Jacobson’s nerve. It also receives special sensory fibers for taste as well as chemoreceptor and baroreceptor afferent input from the carotid body and carotid sinus. Stylopharyngeus muscles are supplied by the motor component, and the parotid gland is supplied by the parasympathetic secretomotor supply. The nerve of Hering is an important branch of the carotid sinus branch, which conveys chemoreceptor and baroreceptor information centrally for circulatory reflux function and may be accountable for the arrhythmogenicity of GPN.
Classically, it is described as a severe transient stabbing pain experienced in the ear, the base of the tongue, tonsilar fossa, or beneath the angle of the jaw. However, the location of the pain can have significantly varied distribution and overlap amongst the nerves supplying the face (trigeminal, vagal, facial). The unusual presentations are cardiac arrhythmias associated with pain episodes, fear to eat (which may be the precipitating cause for pain episode), and syncope.
It must be emphasized that GPN is not as uncommon as reported in the literature due to difficulties in diagnosis, unawareness of the disease and more so with the increasing number of patients with styalgia (pain due to elongated styloid process). It is often compared with trigeminal neuralgia in presentation and incidence due to significant overlap of symptoms and thus causing a diagnostic dilemma.
GPN may be idiopathic with the absence of any obvious lesion. Most cases are mainly recognized as glossopharyngeal nerve compression triggered by a vessel at the root entry zone of the brainstem. Idiopathic causes may be vascular decompression and/or central pontine dysfunction. The secondary cause is a noticeable lesion that includes trauma (skull base fracture, penetrating injury), post-radiation, neoplasm (skull base, cerebellopontine, brainstem, pharynx, tongue, tonsil, metastatic head, and neck tumors), infection (tonsillitis, pharyngitis, petrositis, arachnoiditis, para pharyngeal abscess, and tuberculosis), surgery (post-tonsillectomy, post neck dissection, and post craniotomy), vascular malformations (arteriovenous malformation, fusiform aneurysms, persistent hypoglossal artery, and dissection of the vertebral artery), demyelination (MS), and Eagle’s syndrome as well as others which include direct carotid puncture, choroid plexus overgrowth, and hyperactive dysfunction syndrome. This type of GPN is usually accompanied by numbness or pain around the affected area.
The glossopharyngeal nerve is a mixed cranial nerve with both sensory and motor components. It receives somatic sensory fibers from the oropharynx, posterior third of the tongue, Eustachian tube More Details, middle ear, and mastoid. The sensory supply to the middle ear and mastoid passes along the tympanic branch or Jacobson's nerve. The glossopharyngeal nerve also receives special sensory fibers for taste in the posterior third of the tongue as well as chemoreceptor and baroreceptor afferent inputs from the carotid body and carotid sinuses respectively. The motor component supplies the striated muscle stylopharyngeus and secretomotor parasympathetic fibers to the parotid gland. The other important branch is the carotid sinus nerve (Nerve of Hering) that supplies the carotid body and carotid sinus. It conveys chemoreceptor and stretch baroreceptor information centrally for respiratory, circulatory reflex function and may be responsible for arrhythmogenicity of GPN.
Life-threatening complications of GPN
Harris et al. (1921) reported that GPN could be associated with cardiac dysrhythmia and instability. This relationship is well-accepted and has been documented by many authors. The various reports and case studies have been compiled and summarized by Ferrante et al. Intense irritability and hyper-stimulation of glossopharyngeal nerve feedback onto the nucleus of the tractus solitarius of the midbrain and via collaterals reach the dorsal motor nucleus of the vagus nerve. This activation of this abnormal loop during severe neuralgic pain would be responsible for the heightened vagal response as cardiac dysrhythmia, bradycardia, and hypotension, with cerebral hypoxia, slowing of EEG activity, syncope, and convulsions. Convulsive movements, limb clonus, automatic smacking movements of the lips, and upward turning of the eyes are signs of cerebral hypoxia induced by the bradycardia. The cardiovascular phenomenon is seen during the pain attack or immediately following it. Both pharmacotherapy and surgical treatment eliminates these. There is a subset of patients with demonstrable cardiac manifestations without typical neuralgic symptoms who have responded very well to glossopharyngeal nerve avulsion or MVD. Such syndromes have been called non-neuralgic GPN, in recognition of the fact that glossopharyngeal nerve irritability may not always give rise to pain.
No comments:
Post a Comment