Tinnitus, defined as the perception of noise in the absence of an acoustic stimulus, is a frequent condition with a prevalence of around 14% for males of 60 years or older. A wide variety of interventions are proposed but none of these is consistently effective. Animal data suggest that tinnitus is mediated by cochlear glutamate N‐methyl‐D‐aspartate (NMDA) receptors and is reversed by localapplication of NMDA antagonists. Only two clinical trials with modulators of NMDA neurotransmission have been published but gave opposite results.
We present acase which suggests that NMDA antagonists may be efficacious for a subset of individuals with tinnitus who may be identified by inquiring about tinnitus responsive-ness to medical events that required individuals to besedated with anesthetics.
Case Report
Mr. V. is a 64‐year old man with Behcet's s disease since 1988, a generalized systemic relapsing vasculitis of the arteries and veins of unknown origin. Mr. V., presented cardinal signs of disease, such as eye inflammation, oral and genital ulcerations and characteristic skin lesions, and also presented with aortic aneurysm, multiple recurrent venous thromboses, and gastrointestinal involvement. Treatment with oral prenisone 11 mg/day, azathioprine50 mg/day, and fondaparinux 7.5 mg/day normalized inflammatory markers (CRP = 0.3 mg/mL, Hb = 14.3 g/L, and platelet count = 241 000) but did not fully prevent episodic manifestations, mostly superficial venous thrombosis. Comorbid hypertension was treated with amlodipine 10 mg/day, amiloride 5 mg/day, hydrochlo-rothiazide 50 mg/day, and atenolol 100 mg/day, and the renal function was normal. Comorbid recurrent depressive disorder required a regular psychiatric care and periodic antidepressant treatment.
Mr. V. had several colonoscopies (1988, 2004, 2008, 2011) in order to prevent malignant transformation of colorectal polyps; after the third colonoscopic examina-tion, he mentioned that, immediately after waking from anesthesia, he noticed that his tinnitus had completely disappeared for the following 10 days. Yet, the tinnitus was continuously present during the week before colonoscopy. This phenomenon prompted our interest in a symptom usually shaded by other predominant and acute manifestations of Behcet's disease.
In order to systematically evaluate his condition, we used the case history questionnaire of the Tinnitus Research Initiative. Mr. V. disclosed that her mother also complained of tinnitus. Tinnitus appeared gradually in 1998 and initial onset was related to physical efforts. It had been permanently perceived inside the head, and had been sounding like a very high- pitched hissing without pulsate pattern. Loudness progressively increased along the day to reach a very loud intensity around 4PM. He had been both aware and distressed by his tinnitus for more than 80% of his awake time. Tinnitus was worsened by loud noises and stress, and reduced by music and ambient sounds. While Mr.V. was saying that it was reduced when he had a good sleep at night, he did not find that day naps were changing anything. The head and neck movements did not affect it neither. He did not complain of hearing problems but had found that usual sounds were hurtful and uncomfortable. Mr. V. was used to experiencing pain due to disseminated ulcerations and cervical arthrosis. He did not suffer from vertigo and was not aware of a temporomandibular disorder.
He was receiving medications that were partially relieving his tinnitus: piribedil, 100 mg/day, and clonaze- pam 2.5 mg/day. He was also receiving 3 200 mg/day of gabapentin for his chronic pain and felt that this drug helped him to feel more indifferent to his tinnitus. During the past 12 years, he had never experienced a total disappearance of his tinnitus before his last colonoscopy.
Information was sought after his gastroenterologist, who wrote back that Mr.V. only received a total dose ofpropofol (Diprivan® ,AstraZeneca®) of 400 mg for moderate to deep sedation, provided by an anesthesia specialist. He had no premedication and the monitoring of vital signs did not show hypotension or oxygen desaturation. A pubmed search disclosed the pharmacological properties of propofol and it was hypothesized that tinnitus‐suppressant effect of propofol may be mediated by NMDA antagonism. We looked for other available medications with NMDA antagonism properties through computerized literature search and proposed Mr. V. a trial of 100 mg/day of amantadine. After 1 month of treatment, he returned and reported that tinnitus had completely disappeared after 4 days. But he complained of severe constipation that he could not accept because he had risks of colic perforation. Treatment with physostigmine reduced his constipation but Mr. V. decided to stop taking amantadine. A carryover effect was then observed as tinnitus reappeared only 3 months after treatment removal. For the last 3 years, Mr. V. had been free of tinnitus with 1‐month amantadine treatment every 4 months.
Discussion
Audio‐vestibular disturbance are frequent in patients with Behçet's disease and may be related to severity of Behcet's disease. Mr. V. had normal inflammatory biomarkers. Gastrointestinal involvement gave the oppor-tunity of repeated endoscopic examinations. To our knowledge, there was another case report of a transient interruption of tinnitus following anesthesia by fentanyland propofol. In this case, tinnitus disappeared for 10 days after anesthesia.
The prevalence of frequent tinnitus is considered to be highest among adults with hypertension or major depressive disorder. Hypertension and mood disorders are frequent adverse effects of chronic corticosteroid
treatment. Propofol's hypotensive effect may have contributed to relieve tinnitus. Nevertheless, Mr V. had normal blood pressure for the last 10 years under treatment; moreover, tinnitus' severity was not related neither to depression nor antidepressant treatment during the 15 years follow‐up.
Propofol may also have potentiated clonazepam's effect on tinnitus through GABA agonism but, on theother side, amantadine may also antagonize GABA activity. Propofol is a general anesthesia that selectively modulates glutamatergic transmission via phosphoryla-tion‐mediated down‐regulation of glutamatergic synaptictransmission. Glutamate is the main excitatory neuro-transmitter in both the cochlea and the central auditory pathways and experimental data have suggested that glutamate NMDA receptors may be involved in the generation and maintenance of tinnitus. Amantadine is an uncompetitive NMDA receptor antagonist that is used for the treatment of Parkinson's disease; it has been demonstrated that different NMDA antagonists do not have the same potency in different brain structures and this may contribute to explain why another NMDA antagonist, memantine, did not show evidence of tinnitusimprovement in a controlled study.
Thus, the NMDA hypothesis seemed to be the most parcimonious explanation for the transient disappearance of tinnitus using propofol and its durable suppression with amantadine, and fitted best with available clinical data. As propofol is being increasingly used for gastrointes-tinal endoscopy, which is a frequent medical investiga-tion, it may be useful to systematically ask patients with tinnitus about post‐sedation effects on it. The high safety profile and very short half‐life of propofol may authorize the development of a test of tinnitus sensitivity to NMDA antagonists.
Conclusion
NMDA antagonists such as amantadine may be tried on an individual basis, while gathering data of controlled trials in a subpopulation of patients with propofol‐positive tinnitus.
Corresponding Author:
Prof. Roland Dardennes, MD, MS, Hôpital Sainte‐Anne—Clinique desmaladies mentales et de l'encéphale, 100 rue de la santé, Cedex 14, Paris 75674, France
Email: r.dardennes@ch‐sainte‐anne.fr