LETTER TO EDITOR
|Year : 2015 | Volume
| Issue : 2 | Page : 259--260
Symptomatic improvement of traumatic dysgeusia from an occipital nerve block
Vaibhav Rastogi, Atish Patel, Abhishek D Lunagariya, Vishnumurthy Shushrutha Hedna
Department of Neurology, University of Florida, Florida, USA
Vishnumurthy Shushrutha Hedna
Department of Neurology, University of Florida, Florida
|How to cite this article:|
Rastogi V, Patel A, Lunagariya AD, Hedna VS. Symptomatic improvement of traumatic dysgeusia from an occipital nerve block.Neurol India 2015;63:259-260
|How to cite this URL:|
Rastogi V, Patel A, Lunagariya AD, Hedna VS. Symptomatic improvement of traumatic dysgeusia from an occipital nerve block. Neurol India [serial online] 2015 [cited 2020 Jun 2 ];63:259-260
Available from: http://www.neurologyindia.com/text.asp?2015/63/2/259/156298
Gustation (taste sensation) is one of the primary sensory modalities. Distorted taste sensation or "dysgeusia" is a multifactorial disorder that has varied underlying etiologies including trauma, infection, ageing, the presence of a neurological disorder, malignancy, or inflammation, the adverse reaction to various medications and an iatrogenic precipitation.  Occipital nerve blocks have been used for decades to ameliorate headaches, including the occipital neuralgia. The greater and lesser occipital nerves are the main targets of therapy with the site of injection being at the mastoid process and the superior nuchal ridge, respectively.  However, the alleviation of dysgeusia from an occipital nerve block has never been documented in the literature.
A 43-year-old Caucasian female patient, with a past medical history of mitral valve prolapse and migraine, presented with the sudden onset of dysgeusia that had been persistant for the last 2 months. These symptoms were preceded by an injury precipitated by lifting of a heavy weight that had strained muscles at the nape of her neck. Her lack of taste sensations along with the mild numbness and tingling sensation over her tongue were noticed the day following her injury. The patient was initially evaluated at an oromaxillary clinic 1 week after the onset of symptoms. The evaluation documented the patient's inability to taste sweet, sour, or salty foods over her entire tongue, with some paresthesia that initially started at the posterior aspect of her tongue, and eventually spread over its entire surface. After an oral pathology had been ruled out, she was referred to neurology for further work-up. During her evaluation at the neurology clinic, she denied the presence of any dysphagia, dysphonia, dyspepsia, facial paresthesia, or visual disturbances. Her physical exam was unremarkable except for the loss of taste sensations that had slightly improved over time. There was no history of strokes, seizures, recent viral illnesses, gastrointestinal ailments, or focal limb, trunk or facial weakness or numbness. Her medications included over-the-counter nutritional supplements and aspirin. Her brain and neck magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) ruled out any cerebrovascular events including an arterial dissection, a cerebral infarction, or the presence of a space-occupying lesion. All medications and supplements that she had been taking were withheld for 3 weeks to rule out a peripheral nerve damage secondary to her medication but this did not alleviate her dysgeusia. At a follow-up visit, 2 months after the initial ictus was noticed, the patient found no improvement in her symptoms. She also complained of recurrent episodes of right occipital pain that scored 7 out of 10 on the visual analog scale. Consequently, a right occipital nerve block with dexamethasone was performed that completely resolved the occipital neuralgia. More interestingly, however, was also the complete resolution of her dysgeusia immediately after the nerve block. The patient was able to appreciate salty, sweet, and sour sensations immediately after the procedure.
The simultaneous improvement in both the occipital neuralgia and dysgeusia within minutes of an occipital nerve block indicates that there was a correlation between the administration of the nerve block and the improvement in dysguesia. The chorda tympani nerve (a branch of the facial nerve) accounts for taste sensations on the anterior two-thirds of the tongue. The fibers of chorda tympani course in the lingual nerve (a branch of the mandibular division of the trigeminal nerve). Since some afferent fibers of the lingual nerve also course in the hypoglossal nerve through the C (cervical vertebrae) 2 spinal nerve root,  we believe that the latter can easily be damaged during neck trauma and may precipitate dysgeusia. The chorda tympani nerve also has interconnections with the glossopharyngeal nerve.  Thus, the indirect traumatic affliction of fibers of the chorda tympani nerve by the mechanism stated above may also inhibit afferent fibers transmitted through the glossopharyngeal nerve. This may also cause loss of taste sensations on the posterior one-third of the tongue.
The mechanism by which the occipital nerve block improved dysgeusia is not known. There are two proposed hypotheses. A remote possibility could be related to the extravasation of steroid though the tissue planes affecting the nerves in the vicinity. According to this, the chorda tympani nerve unites with the facial nerve in the facial canal just proximal to the level of stylomastoid foramen. There is a possibility that the injection site that was in close proximity to the mastoid process resulted in the solution spreading through the tissue planes to the stylomastoid foramen and thus to the facial nerve and its chorda tympani branch. The steroid relieved the post-traumatic facial nerve edema and its compression within its canal. ,, The second hypothesis relates to the suppression of ephatic transmission and the restoration of normal transmission in all the related nerves and their interconnections that are connected with the perception of taste sensations. The hypoglossal nerve has connections with the C2 spinal nerve. Since the afferent fibers of the lingual nerve travel in the hypoglossal nerve,  there is a possibility that they may also possess connections with the C2 spinal nerve roots. The greater and lesser occipital nerve also arise from the second spinal nerve. The steroid block for the occipital neuralgia stabilized the transmission of impulses within the related interconnected nerves including the occipital nerve, the C2 spinal nerve root, the hypoglossal and the lingual nerve (the latter containing the afferent fibers from the chorda tympani nerve that carry taste sensations from the anterior two-thirds of the tongue) leading to improvement in dysgeusia. , Post-traumatic misdirectional regeneration of facial nerve fibers can result in a cross-talk between the facial nerve and the cervical plexus (and the occipital nerve in particular).  Suppression of these direct interneural connections by an occipital block could have resulted in the recovery of the dysgeusia.
In conclusion, occipital nerve block may be effective in the resolution of traumatic dysgeusia; however, the mechanism of action is unclear. Further in-depth studies are required to assess the role of occipital nerve block in the amelioration of dysgeusia.
We would like to extend our appreciation to the patient for allowing us to carry out this work and to all those who participated in her interdisciplinary care.
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