Auditory and Electrophysiological Patterns of a Unilateral Lesion of the Lateral Lemniscus

Abstract

Auditory disorders resulting from focal brainstem lesions are rarely symptomatic. Isolated lesions of the inferior colliculus have previously been reported, whereas no detailed description of a localized involvement of the lateral lemniscus is yet available. We report a unilateral lesion of the lateral lemniscus by a bleeding in a cavernoma. Symptoms included strictly contralateral tinnitus and auditory impairment, with normal pure-tone and speech audiometry. Conversely, the dichotic listening test revealed an extinction of contralateral ear input. The brainstem auditory evoked potentials disclosed a reduced and delayed wave V only after contralateral ear stimulation, while the middle latency evoked potentials were normal. This observation shows that a unilateral lesion of the lateral lemniscus can produce auditory symptoms. The dysfunction of auditory pathways is associated with specific electrophysiological abnormalities that can be assessed by evoked potential recording.

Inactivation of cerebellar output axons impairs acquisition of conditioned eyeblinks

“…Because our paradigm utilized an auditory CS, possible involvement of the LL in explaining our present results has to be considered. Although the LL does not appear to be involved in pure tone discrimination (Cho et al 2005), it can not be excluded that its inactivation could alter the neural representation of the bilateral acoustical CS and potentially retard the rate of CR acquisition, as shown in a study that examined effects of bilateral LL lesions (Steinmetz et al 1987). Therefore we tested LL involvement in a separate group of animals.…”

Hearing disorders in brainstem lesions

“…Lee et al (2008) described normal speech and pure-tone audiometry, normal tympanometry, and acoustic reflexes but hyperacusis in a case of right pontine hemorrhage involving the lateral lemniscus; 516 G.G. CELESIA Cho et al (2005) in a pontine hemorrhage noted normal speech and pure-tone audiometry while dichotic listening testing revealed an extinction of contralateral ear input. Levine et al (1993) noted that a unilateral lesion in the region of the lateral lemniscus affected IATD for low-frequency stimuli.…”

“…Bellis (2003) advocates the use of masking level difference (MLD) as the: "most (Olsen et al, 1976;Lynn et al, 1981;Musiek et al, 1989;Pillion et al, 2008). Others have claimed that dichotic listening testing is an effective alternative to analyze brainstem auditory function (Hariri et al, 1994;Fischer et al, 1995;Cho et al, 2005). Musiek et al (2011) studied the sensitivity, specificity, and efficiency of commonly used behavioral central auditory processing test batteries in 20 individuals with known lesions of the central auditory nervous system and related auditory symptoms.…”

“…Diseases of the brainstem usually involve many structures, producing a plethora of neurologic deficits (Haymaker, 1969;Voordecker et al, 1988;Urban and Caplan, 2011), often relegating "auditory symptoms in the background" (Cho et al, 2005). Rarely, a small lesion is limited to the auditory system.…”

“…Unilateral lesions of the lateral lemniscus have been reported to be clinically silent on standard testing, but their effects can be revealed using careful psychoacoustic testing (Table 29.4), which shows abnormal sound localization and interaural time perception (Levine et al, 1994;Hausler and Levine, 2000;Cho et al, 2005). Lee et al (2008) described normal speech and pure-tone audiometry, normal tympanometry, and acoustic reflexes but hyperacusis in a case of right pontine hemorrhage involving the lateral lemniscus; 516 G.G.…”