Palatal myoclonic tinnitus is an extremely rare type of tinnitus caused by voluntary or involuntary contraction of palatal muscle. Two discrete forms have been identified, namely a 'symptomatic'form or an 'essential' form. A symptomatic palatal myoclonic tinnitus which develops secondary to tumorous, ischemic or degenerative lesions of the brainstem or the cerebellum is less common and is usually observed in middle aged patients with a predominant tendency to males [2]. Essential palatal myoclonic tinnitus in which no structural lesion is discernable, is more common and prominent than the secondary form, and usually presents to otolaryngologists with the symptom of a loud clicking type of tinnitus. It commonly occurs with a mean age of 20s but may also occur in childhood with the same gender proportion and mostly continues without therapy; however, may disappear spontaneously in a rare occasion. The etiology of either form of palatal myoclonus still remains unclear and presumably involves a dysfunction (essential) or a lesion (symptomatic) of the connections between the dentate nucleus, red nucleus and inferior olivary nuclei, which is called the Guillain-Mollaret triangle.

The proper diagnosis of essential or secondary palatal myoclonic tinnitus is most often made by the observation of palatal myoclonic movement under endoscopic examination and the auscultation of clicking tinnitus with Toynbee tube. Neurological examination and imaging study are necessary to exclude a brain lesion which would lead to a diagnosis of secondary palatal myoclonus. Hyperactive palatal myoclonic contraction can be detected and documented by an electromyogram (EMG) (Fig. 1A). Several therapeutic strategies have been demonstrated to relieve symptomatic clicking tinnitus with varying therapeutic results of success and/or adverse effects.

Medical treatment has used anti-convulsatants, muscle relaxants, benzodiazepines, barbiturates, and anti-cholinergic agents, but no drug has been shown to significantly improve symptoms reproducibly. Surgical therapies including sections of the levator veli palatini muscle and the tensor veli palatini muscle, have also provided highly variable results and also run a high risk of side effects. Recently, the most popular, safe and effective therapeutic tool for palatal myoclonic tinnitus has been the injection of botulinum toxin to the palatal muscles. Promising results have been shown in various case reports (Table 1) [3456]. Known side effects of botulinum toxin injection to palatal muscles are velopharyngeal insufficiency, hypernasal voice (rhinophonia), and temporary dysphagia due to the excessive neuromuscular inhibition of the adjacent muscles of the palate. To reduce side effects, toxin dosage should be as high as necessary, but as low as possible. EMG-guided injection can be useful to achieve effective injection of toxin with the avoidance of side effects to target the muscles of the palatal myoclonic tinnitus (Fig. 1B). Recent data from our tinnitus clinic has shown the development of essential palatal myoclonic tinnitus in younger ages (mean 27.9 years) without gender difference. Many of these cases were accompanied by middle ear myoclonic tinnitus (43.9%). Conservative therapy, using behavioral therapy and reassurance along with medication using anticonvulsants, muscle relaxants, and anxiolytics for 3 months has demonstrated satisfactory results in over 80% of the patients. However, patients with intractable palatal myoclonic tinnitus were treated by botulinum toxin injection, either EMG-guided or not, and were completely cured without significant long lasting side effects [7].

Tinnitus secondary to middle ear myoclonus is very rare, and consequently there are very few reports of it in the English literature [89101112]. It has been suggested that the crackling or buzzing sounds reported are caused by repetitive and abnormal tensor tympani and stapedial muscles contractions [11]. These myoclonic movements are thought to be a form of segmental myoclonus involving brainstem innervated muscles. Vascular, infectious and demyelinating disorders as well as anxiety, trauma and neoplastic disease have all been implicated in the etiology of segmental myoclonus [91112]. In a previous report of the largest case series of middle ear myoclonus, 58 enrolled patients had a mean age of 29.8 years (range, 6-70 years) and 20.7% (n=12) were less than 10 years old [12]. Stressful events or noise exposure were frequently associated with the onset of middle ear myoclonic tinnitus, which indicates that a possible pathological mechanism of the middle ear myoclonic tinnitus could be brain reorganization due to stress, noise or brain lesions. Middle ear myoclonic tinnitus can also be associated with vigorous contractions of the eyelid, called forceful eyelid closure syndrome [14], or with palatal myoclonus [12].

Impedance audiogram and otoendoscopic examinations of the tympanic membrane are helpful tools for diagnosing middle ear myoclonic tinnitus. Inward-and-outward motion, mostly in the posterior part of the tympanic membrane can be observed on otoendoscopic examination. Sound evoked tremor-like motion of the tympanic membrane, which is also frequently observed in an acoustic reflex decay test or strong inward-and-outward motion of the tympanic membrane in the middle ear myoclonic tinnitus associated with forceful eyelid closure syndrome are useful objective tools for diagnosing MEM tinnitus (Fig. 2). Tympanometry can confirm rhythmic changes in the middle-ear compliance in patients with middle ear myoclonic tinnitus [13]. Diagnostic tools useful for middle ear myoclonic tinnitus are summarized in Table 2.

Medical treatment with an anticonvulsant, i.e. cabarmazepine, a muscle relaxant or a sedative agent have all been reported to produce partial to complete relief of symptoms in middle ear myoclonic tinnitus [1415].

In addition, more than 75% of patients exhibited complete or partial remission of their symptom using combination medical therapy [12]. Other therapeutic options like white band noise masking devices were also successful in treating middle ear myoclonus [16]. Botulinum toxin placed on a piece of gelfoam socked form and inserted through a perforation of the tympanic membrane into the middle ear cavity of a patient suffering stapeius myoclonic tinnitus was able to provide disappearance of symptoms for 3 months, indicating the possible therapeutic tool of botox toxin for middle ear myoclonic tinnitus [17]. Patients with intractable middle ear myoclonic tinnitus who underwent sectioning of the middle ear tendons showed very good outcomes [18]. Sectioning of middle ear tendons (both tensor tympani and stapedius) via a transmeatal approach in 11 ears with intractable tinnitus resulted in complete resolution or marked improvement of the symptom in all cases, demonstrating surgical sectioning of middle ear tendons to be successful in treating intractable middle ear myoclonic tinnitus [12]. Considering the high response rate to medical therapy, clinicians should prescribe medication as a first-line management of this disorder. If medical therapy fails, surgical sectioning of the tendons of the middle ear muscles is a good second-line management procedure.

A detailed history of pulsatile tinnitus is essential to diagnose the possible cause of vascular tinnitus. Throbbing, rushing, or humming sounds synchronized with the pulse suggests a vascular etiology. Thorough physical examinations through otoscopy, auscultation of the ear canals, and a full head and neck examination should be performed. A tympanic mass could be visible on otoscopy or microscopic examination. To discriminate venous causes of vascular tinnitus, the ipsilateral internal jugular vein (IJV) can be gently compressed and any changes in tinnitus loudness reported. A head turning test is also used to confirm the venous etiologic vascular tinnitus along with the compression maneuver. In tinnitus of venous origin, light digital pressure over the ipsilateral IJV or head turning towards the tinnitus side elicits the tinnitus to diminish or subside.

Audiometric tests should include pure tone audiometry and tympanometry. Tympanometry is useful to diagnose middle ear effusion and other associated conductive hearing loss. Auditory evoked brainstem responses are useful in patients suspected of having benign intracranial hypertension in which cases prolonged interpeak latencies are the most common abnormal findings [25]. A full blood count, vitamin B12, and thyroid function tests should be performed to exclude hyperhemodynamic causes of anemia or hyperthyroidism. Cholesterol level is useful to check for hyperlipidemia, a risk factor for atherosclerosis.

To select an imaging study, the potential etiology of venous or arterial origin can be a determining factor for choice of imaging. Temporal bone computed tomography, or brain magnetic resonance venography (MRV) would be a first line of imaging study for venous-origin vascular tinnitus whereas transcranial Doppler sonography or brain CT angiography or brain magnetic resonance angiography (MRA) will differentiate arterial-origin vascular tinnitus (Fig. 3) [26]. For the rare cause of vascular tinnitus, an aneurysm of brain vessels, angiographic confirmation followed by concomitant radiological intervention with coil or other materials have been reported [27].

A diagnostic algorithm for vascular tinnitus has been suggested in our previous report [22]. Pulsatile tinnitus should be called idiopathic only after an extensive work-up has been completed and a specific diagnosis has not been reached. Thorough history taking and physical examination as well as individualized diagnostic testing are important factors in evaluating patients with pulsatile tinnitus (Table 4).

Saline was the most commonly used topical treatment, but historical formulas such as salicylic and boric acid powder (in a 1:4 proportion), diluted hydrochloric acid, chlorobutanol, and benzyl alcohol and saturated potassium iodide solution have been studied [353637].

Results ranged from 63.5% to 100% partial or full resolution of symptoms without consistent effectiveness among the previous reports.

The symptoms of PET are postulated to arise from tympanic membrane movement, thus techniques to weigh down the TM have been attempted. Tympanostomy tube insertion was the most frequently described method with the results ranging from 53-100% of patients achieving partial or full resolution of the symptoms of PET [3538]. Sniffing to alleviate PET symptoms should be requested and the attic retraction of the tympanic membrane as well as the inward-and-outward motion of it should be checked to detect the relationship between sniffing and PET. Ikeda et al. reported the tympanostomy tube insertion was more effective in patients of PET with sniffing habit than those without [35]. No serious adverse events except temporary otorrhea or acute otitis media have been reported.

Recently, mass loading of the tympanic membrane using tympanic membrane paper patching has been reported with the success rate of PET symptom control up to 76.2% [39]. Patients responding to the paper patching of tympanic membrane can be treated with permanent augmentation of the tympanic membrane with cartilage tympanoplasty to alleviate PET symptoms [40]. Patients who exhibit a flaccid tympanic membrane segment with the symptom of PET and are good responders to paper patching are more appropriate for cartilage tympanoplasty.

To prevent the movement of air through an abnormally open ET, transtympanic, transnasal or transoral occlusion of the ET opening has been attempted. Different techniques such as ET plugging, cautery of the ET orifice, or injection of bulking substance at the ET orifice have been introduced with variable therapeutic results [41424344]. Plugging of the ET via transtympanic or transnasal approaches has been reported and the devices used include transvenous angiocatheter or silicone plug [424344]. Eustachian tube injection was frequently applied to PET patients as a method of occlusion of ET orifice. Injectable materials included Teflon, silicone, gelatin sponge, a polytef paste, fat and cartilage [454647]. Cautery of the ET orifice to promote scarring using silver nitrate, diathermy or KTP laser has been introduced to relieve PET symptoms with mixed results. Serous otitis media were reported as a complication with the ET cautery procedure [484950].

To date, there has been no simple and single satisfactory solution for patients with PET. However, with the proper diagnosis of PET, patients suffering from their aural fullness and autophony can be managed successfully with various types of therapeutic modalities.