If bilateral tinnitus is the basis of persistent complaints, one often discovers that the patient is anxious or depressed, in which case a careful history will reveal the other features of these disorders. Treatment then must be directed to the psychiatric symptoms. In their review, Lockwood and colleagues suggest that all patients with undifferentiated tinnitus be protected from loud sounds and ototoxic drugs (the main ones being aminoglycoside antibiotics, certain loop diuretics, neurotoxic chemotherapies such as cisplatin, and perhaps high doses of aspirin). The American Tinnitus Association website may be helpful to some patients as a source of reassurance (http://www.ata.org).
Tinnitus that is unilateral, pulsatile, or fluctuating and associated with vertigo should be investigated by appropriate neurologic and audiologic studies.
Other Disorders of Auditory Perception
On occasion, pontine lesions may be accompanied by complex auditory illusions, sometimes with the qualities of true hallucinations (pontine auditory hallucinosis) as in the patients, one of whom was ours, described by Cascino and Adams. These consist of alternating musical tones, like those of an organ; a jumble of sound, like a symphony orchestra tuning up; or siren-like or buzzing sounds, like a swarm of bees. These auditory sense disturbances are more complex than neurosensory tinnitus but less formed than temporal lobe hallucinations. They are usually associated with impairment of hearing in one or both ears and other neurologic signs related to the pontine lesion. An unpleasant degree of hyperacusis in the contralateral ear has also been reported with upper pontine tegmental lesions. BAEPs reveal intact cochlear, auditory nerve, and cochlear nuclear responses. As in the case of peduncular visual hallucinosis, patients realize that the sounds are unreal, that is, they have insight into their illusory nature.
Another well recognized but inexplicable type of auditory hallucinosis occurs in elderly patients with longstanding neurosensory deafness. All day long, or for several hours at a time, they hear songs, symphonies, choral music, or familiar or unfamiliar melodies interrupted only by other ambient noise, sleep, or conversations that engage their attention. The “choice” of music has been referable, not surprisingly, to the individual’s earlier life. Our patients, like those reported by Hammeke and colleagues, have been neither depressed nor demented, and antiepileptic and neuroleptic drugs have had no effect. Activation of the right auditory cortex on single-photon emission tomography (SPECT) and magnetoencephalography has been reported in such a case by Kasai and colleagues. The problem may be analogous to the one of Charles Bonnet syndrome, in which elderly individuals with failing vision experience rich visual hallucinations. We find it puzzling that pontine lesions are implicated in some cases, as mentioned previously.
Complex auditory hallucinations may occur as part of temporal lobe seizures arising from a variety of temporal lobe lesions. Conversely, seizures may be induced by musical sounds as well as by other auditory stimuli. These topics are discussed in Chaps. 15 and 21. Paracusis, a condition in which a sound, tune, or a voice is repeated for several seconds, is also a cerebral auditory phenomenon, similar in a sense to the visual phenomenon of palinopsia. The precise anatomy is unknown. The auditory hallucinations of schizophrenia have been extensively studied in relation to activity of the temporal lobes, as discussed in Chap. 49.
Another phenomenon commented on here casually is the phenomenon of repeatedly experiencing parts of a recently heard song or melody, an “ear worm.” The problem is self-limiting but occasionally becomes a chronic medical complaint akin to auditory hallucinosis, probably an obsessive complaint but rarely attributed, on uncertain grounds, to temporal lobe seizures.