- Division of Functional Neurosurgery, Department of Neurology, Hospital das Clinicas, University of São Paulo Medical School, São Paulo, Brazil
Iuri Santana Neville
Division of Functional Neurosurgery, Department of Neurology, Hospital das Clinicas, University of São Paulo Medical School, São Paulo, Brazil
DOI:10.4103/2152-7806.154452Copyright: © 2015 Schroeder HK. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Schroeder HK, Neville IS, de Andrade DC, Lepski GA, Teixeira MJ, Duarte KP. Microvascular decompression of the posterior inferior cerebellar artery for intermediate nerve neuralgia. Surg Neurol Int 01-Apr-2015;6:52
How to cite this URL: Schroeder HK, Neville IS, de Andrade DC, Lepski GA, Teixeira MJ, Duarte KP. Microvascular decompression of the posterior inferior cerebellar artery for intermediate nerve neuralgia. Surg Neurol Int 01-Apr-2015;6:52. Available from: http://sni.wpengine.com/surgicalint_articles/microvascular-decompression-posterior-inferior-cerebellar-artery-intermediate-nerve-neuralgia/
Background:Intermediate nerve neuralgia (INN) is an extremely rare craniofacial pain disorder mainly caused by neurovascular compression.
Case Description:We present the case of a 48-year-old female with a 20-month history of intractable paroxysmal INN on the right side. The patient described feeling paroxysmal pain in her auditory canal, pinna, deep in the jaw, and adjacent retromastoid area on the right side. She described the pain as being like a burning sensation. Magnetic resonance imaging showed the right posterior cerebellar artery crossing the cerebellopontine cistern in close contact with the right VII and VIII nerves. Surgical exploration via retromastoid craniotomy revealed vascular compression of the intermediate nerve by the posterior cerebellar artery. We therefore performed microvascular nerve decompression to relieve pain, and the patient remained pain-free at the 6-month follow-up visit.
Conclusion:INN should be considered as a differential diagnosis in cases with atypical facial neuralgia, and microvascular decompression is an effective treatment option that can provide optimal pain relief.
Intermediate nerve neuralgia (INN) is an extremely rare craniofacial pain disorder, which tends to affect middle-aged patients and can be a debilitating pathology due to its refractoriness to medical treatment and its negative impact on quality of life. INN always manifests unilaterally and is characterized by severe paroxysms of stabbing electric shock-like and lancinating pain felt deep in the auditory canal, the external structures of the ear, the palate, tongue, or deeply in the facial musculature. The pain is usually intermittent and may last seconds to minutes.[
There are several theories aimed at explaining the cause of this and other cranial neuralgias. Often, the nerve can be compressed by a nearby blood vessel, and this condition is called nerve–vessel conflict or neurovascular conflict.[
Pharmacotherapy is the first line of treatment for INN as well as other cranial neuralgias. However, medications are not always fully effective, and their effectiveness may even decrease over time, with long-term use causing resistance. Furthermore, some of these medications may cause disabling side effects. In patients who do not respond favorably to pharmacotherapy or who have nerve–vessel conflicts, surgical treatment may be necessary.[
Since the first case report of INN by Clark and Taylor[
Here we report an unusual case of compression of the nervus intermedius by the posterior inferior cerebellar artery (PICA). The patient experienced immediate pain relief after MVD.
The patient was a 48-year-old female with a 20-month history of right-sided orofacial pain. Her main complaint was paroxysmal pain in her auditory canal, pinna, deep in the jaw, and adjacent retromastoid area on the right side. The pain was described as a burning sensation in an area located in the posterior external auditory canal wall and was elicited by chewing, touch, or contact with objects or warm water. It usually lasted for a few seconds to 1–2 min and would remit spontaneously and abruptly. The patient ranked it 10 on the numeric rating scale. She had no odynophagia and was treated with carbamazepine (maximum 1200 mg/day), which proved to be ineffective. Other medications (Sertraline, Amitriptyline, and Pregabalin) also failed to provide clinically significant pain relief. The patient's otoscopic examination was unremarkable bilaterally. There was no sensory loss, facial palsy, or other neurological signs.
The patient underwent preoperative MRI and MRI angiography, including 3D T2-weighted fast spin echo and 3D constructive interference in the steady-state (CISS) sequences. Images showed the right posterior cerebellar artery crossing the cerebello-pontine cistern [arrow in
A right-sided suboccipital retrosigmoid craniotomy was performed. The patient was put in a left lateral decubitus position, with the head well rotated and fixed in a Mayfield clamp. The dura was opened. Minimal retraction of the cerebellum was performed to achieve cerebrospinal fluid (CSF) drainage. In the cerebello-pontine angle, as shown in
Following the decompression, the patient had an uneventful postoperative recovery and the pain resolved immediately with no additional neurological deficits, demonstrating that the compression was the only cause of pain. Postoperative CT scans were unremarkable. Medication was tapered off in the first few weeks after surgery. At 6-months’ follow-up, no further paroxysmal pain had occurred.
The nervus intermedius, also known as the intermediary nerve, intermediate nerve or Wrisberg's nerve, was first identified in 1563, but was described in great detail and named by Heinrich August Wrisberg in 1777 as “portio media inter comunicantem faciei et nervum auditorium.”[
In 2004, the International Headache Society (IHS) classification set out obligatory requirements for the diagnosis of intermedius neuralgia: The presence of paroxysmal pain with a trigger area in the posterior external auditory canal wall. In fact, the clinical diagnosis is based on pain description and classified as nervus intermedius neuralgia.[
Rhoton et al. classified the course of the nervus intermedius into three segments. The medial segment adheres closely to the vestibule-cochlear nerve, whereas the intermediate segment runs separately between the VII and VIII cranial nerves. Finally, the lateral segment joins the motor root of the facial nerve within the internal acoustic meatus.[
There are various types of chronic pain that can affect the ear canal, and the term geniculate neuralgia (GN), or Hunt's neuralgia, has been used extensively to describe them. The nomenclature in the literature is often confusing. GN can follow viral herpes zoster infection at the GG,[
MRI with MRI angiography can help with diagnosis, as it can help identify the causal mechanism of the pain (due to vascular compression of the intermediate nerve) and thus distinguish INN from other pain syndromes that are designated as GN.[
Much has been studied about the current etiology of INN and other cranial neuralgias, but its physiopathology is still poorly understood. Neurovascular compression is INNs main etiology. In this form of neurovascular conflict, the cranial nerve can be compressed by an aberrant loop of artery or vein that is in close proximity to the nerve.[
The close anatomical connection between the anterior inferior cerebellar artery (AICA) and the facial and acoustic nerve complex at its emergence from the brainstem has been confirmed by several clinical reports.[
Drugs may relieve symptoms in many patients, especially in the early stages. Over time, however, drugs may lose their efficacy.[
Sectioning of the nervus intermedius has been used quite extensively. While MVD alone has been demonstrated to be effective in anecdotal reports of good to excellent pain relief, experience with MVD is quite limited.[
INN should be distinguished from the numerous other ear and facial pain syndromes that make up the broader clinical entity of GN. This distinction can guide surgical decision-making toward selective MVD of the intermediate nerve, and thus prevent the untoward effects of ablative and resective procedures on other cranial nerves.[
Because the compressed nervus intermedius can be cured with MVD, we believe INN should be included among the cranial nerve syndromes caused by vascular compression at the REZ of the nerves.[
In conclusion, INN should be considered as a differential diagnosis in cases with atypical facial neuralgia, and MVD is an effective treatment option that can provide optimal pain relief.
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