Traumatic brainstem deafness with normal brainstem auditory evoked potentials

Reversible Hearing Impairment Due to Inferior Colliculi Compression by a Pineal Glial Cyst

Pineal glial cysts associated with bilateral hearing impairment are very rare. Here, we present the case of a 13-year-old boy with a pineal cyst, which caused severe bilateral hearing impairment persisting from 6 years of age. When the patient was 6 years old, the bilateral hearing acuity was about 40 dB on audiometry. Upon admission to our otolaryngology department, his audiogram revealed a bilateral worsening of the hearing acuity (80 dB). Magnetic resonance imaging (MRI) revealed an abnormal pineal cyst with tectal compression from the left with hardly normal bilateral brainstem auditory evoked potentials (BAEPs). We obtained informed consent for exploratory surgery and employed the right occipital transtentorial approach for pineal cyst removal. Based on histological examination, we diagnosed a glial cyst of the pineal gland. At 12 months postoperatively, the patient's hearing improved, showing a bilateral hearing acuity of 40 dB on audiometry. Since the auditory pathway has both crossed and uncrossed fibers at the upper pons and midbrain level, compression at the lateral lemniscus or inferior colliculus level can cause bilateral hearing impairment. In the present case, there was a possible slow pineal cyst growth that eventually compressed the upper pons to the midbrain, lateral lemniscuses, or inferior colliculi from the left side, this eventually led to bilateral hearing impairment. These findings indicate that surgery can improve hearing acuity in patients with a pineal cyst associated with progressive hearing impairment.

Otopathologic Changes in the Cochlea following Head Injury without Temporal Bone Fracture

Objective

Hearing loss following temporal bone (TB) fracture may result from direct transection of the middle and inner ear. The pathophysiology of hearing loss due to head injury without TB fracture, however, is not well understood. Few reports describe otopathologic findings. Herein, we investigate the pathologic findings of patients who sustained a head injury without evidence of a TB fracture.

Study Design

Otopathology study.

Setting

Otopathology laboratory.

Subjects

Subjects with a history of head injury without TB fracture.

Methods

The TBs of patients with head injury were evaluated by light microscopy. Inner ear anatomy was evaluated, including counts of spiral ganglion cells (SGCs), hair cells, pillar cells, atrophy of the stria vascularis, and the presence of endolymphatic hydrops. SGC counts were compared with those of historical age-matched controls.

Results

All cases (N = 6 TBs) had evidence of inner ear pathology. Of the 6 cases, 2 (33%) had severe loss of hair cells in all 3 turns of the cochlea, and 4 (67%) cases demonstrated moderate to severe loss at the basal turn of the cochlea. Four cases had scattered atrophy of the stria vascularis, and 3 (50%) had cochlear hydrops. The number of total SGCs was decreased, with an average 53% loss (range, 25%-79%) as compared with controls. The SGC count loss was evenly distributed along Rosenthal’s canal.

Conclusions

Patients with a history of head injury without TB fracture demonstrate inner ear pathology. Further studies are necessary to determine if otopathology findings are directly attributable to trauma.

Systematic review of hearing loss after traumatic brain injury without associated temporal bone fracture

OBJECTIVE

While hearing loss following temporal bone fracture is a well-described phenomenon, few data exist on auditory dysfunction in patients with traumatic brain injury (TBI) without temporal bone fracture. Herein, we aim to systematically review hearing loss after TBI without bony fracture and describe its etiologies.

DATA SOURCES

Pubmed, Embase, Cochrane databases.

REVIEW METHODS

A systematic review of the literature from 1966 to January 2017 was performed using Preferred Reporting Items for Systematic Reviews and Meta-analyses recommendations. Data were obtained from studies that investigated hearing loss in TBI without skull fracture according to an a priori protocol with inclusion and exclusion criteria. Variables included type and severity of hearing loss, as well as pathophysiology of hearing loss.

RESULTS

There were 13 studies with 773 patients that met study criteria. Overall, there was one prospective cohort study, four retrospective cohort studies, two case-control studies, and six case reports. The studies with the highest level of evidence report a change in hearing of at least 10-15 dB across a range of frequencies in as many as 58% percent of TBI patients without bony fracture, which was transient or chronic. The mechanism/severity of injury may impact the rate of hearing loss.

CONCLUSIONS

Hearing loss after TBI in the absence of bony injury appears to be a clinically significant but poorly characterized phenomenon.

Hearing disorders in brainstem lesions

Auditory processing can be disrupted by brainstem lesions. It is estimated that approximately 57% of brainstem lesions are associated with auditory disorders. However diseases of the brainstem usually involve many structures, producing a plethora of other neurologic deficits, often relegating "auditory symptoms in the background." Lesions below or within the cochlear nuclei result in ipsilateral auditory-processing abnormalities detected in routine testing; disorders rostral to the cochlear nuclei may result in bilateral abnormalities or may be silent. Lesions in the superior olivary complex and trapezoid body show a mixture of ipsilateral, contralateral, and bilateral abnormalities, whereas lesions of the lateral lemniscus, inferior colliculus, and medial geniculate body do not affect peripheral auditory processing and result in predominantly subtle contralateral abnormalities that may be missed by routine auditory testing. In these cases psychophysical methods developed for the evaluation of central auditory function should be employed (e.g., dichotic listening, interaural time perception, sound localization). The extensive connections of the auditory brainstem nuclei not only are responsible for binaural interaction but also assure redundancy in the system. This redundancy may explain why small brainstem lesions are sometimes clinically silent. Any disorder of the brainstem (e.g., neoplasms, vascular disorders, infections, trauma, demyelinating disorders, neurodegenerative diseases, malformations) that involves the auditory pathways and/or centers may produce hearing abnormalities.

Prognostic Value of Evoked Responses and Event-Related Brain Potentials in

The behaviourally unresponsive patient, unable to exhibit the presence of cognition, constitutes a conundrum for health care specialists. Prognostic uncertainty impedes accurate management decisions and the application of ethical principles. An early, reliable prognosis is highly desirable. In this review investigations studying comatose patients with coma of different etiologies were selected. It is concluded that objective prognostication is enhanced by the use of electrophysiological tests. Persistent abnormalities of brainstem auditory evoked potentials and short-latency somatosensory evoked potentials reliably indicate the likelihood of irreversible neurological deficit or death. Meanwhile, the presence of “cognitive” event-related brain potentials (e.g., P300 and mismatch negativity) reflects the functional integrity of higher level information processing and, therefore, the likelihood of capacity for cognition. An approach that combines clinical and electrophysiological values provides optimal prediction of outcome and level of disability.

Speech processing disorder in neural hearing loss

Deficits in central auditory processing may occur in a variety of clinical conditions including traumatic brain injury, neurodegenerative disease, auditory neuropathy/dyssynchrony syndrome, neurological disorders associated with aging, and aphasia. Deficits in central auditory processing of a more subtle nature have also been studied extensively in neurodevelopmental disorders in children with learning disabilities, ADD, and developmental language disorders. Illustrative cases are reviewed demonstrating the use of an audiological test battery in patients with auditory neuropathy/dyssynchrony syndrome, bilateral lesions to the inferior colliculi, and bilateral lesions to the temporal lobes. Electrophysiological tests of auditory function were utilized to define the locus of dysfunction at neural levels ranging from the auditory nerve, midbrain, and cortical levels.

A case of locked-in syndrome complicated by central deafness

BACKGROUND

A 53-year-old male with a history of hypertension, diabetes mellitus, and factor V deficiency presented to an emergency room with progressively increasing headache, slurred speech, and left upper extremity weakness. Over the previous 3 months, he had been receiving warfarin for prophylaxis of deep venous thrombosis following knee surgery. After presentation and an initial period of coma, he became tetraplegic and anarthric, requiring intubation and ventilatory assistance.

INVESTIGATIONS

Neurological examination, CT scan, electroencephalogram, brainstem auditory and visual evoked potential studies, neuropsychological assessment and functional MRI studies.

DIAGNOSIS

Locked-in syndrome following ventral pontine hemorrhage, complicated by central deafness secondary to extension of the lesion to the inferior colliculus.

MANAGEMENT

Development of an augmentative communication system designed to exploit the patient's preserved cognitive and motor functions.

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

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.

Auditory agnosia caused by a tectal germinoma

The authors describe a patient with auditory agnosia caused by a tectal germinoma. Despite having normal audiometric tests, the patient failed to recognize words and musical characters. On head MRI, the inferior colliculi were infiltrated by tumor. Neuropsychological tests revealed severe impairment in recognition of environmental sounds and words, defective musical perception, and stop consonant-vowel discrimination. Inferior colliculus may play a role in the analysis of sound properties.

Sensorineural Hearing Loss and Word Deafness Caused by a Mesencephalic Lesion: Clinicoelectrophysiologic Correlations

OBJECTIVE

To assess the role of inferior colliculi as a generator of Wave V of brainstem auditory evoked potentials and in modulating the olivocochlear efferent auditory system.

STUDY DESIGN

Case review.

SETTING

University and tertiary referral centers.

PATIENTS

Case report of a patient with word deafness caused by mesencephalic hemorrhage according to audiologic and electrophysiologic findings.

RESULTS

The patient is a 48-year-old woman who suffered word deafness caused by hemorrhage localized at the quadrigeminal plate (including the inferior colliculi). At a follow-up visit, her pure-tone audiogram revealed symmetric severe sensorineural hearing loss that had partially resolved, whereas speech audiometry showed persistent word deafness. Acoustic reflexes were elicited, with normal thresholds bilaterally. Transient evoked otoacoustic emissions were recorded from both ears, with normal response and signal-to-noise ratio, but there was a failure for their amplitude to be suppressed with contralateral sound stimulation. Brainstem auditory evoked potentials were of normal amplitude and latencies bilaterally.

CONCLUSION

The finding of normal brainstem auditory evoked potentials supports the view that the neural generator of Wave V lies caudally to the inferior colliculi. Moreover, the abnormal suppression of transient evoked otoacoustic emissions indicates that descending collicular input is capable of modulating levels of excitability within the olivary nucleus and the cochlea.

Reversible hearing loss associated with a malignant pineal germ cell tumor. Case report

In patients with pineal tumors, clinical symptoms are due to direct compression of adjacent structures. The most common signs include increased intracranial pressure (80%) caused by obstruction of the sylvian aqueduct, and Parinaud syndrome (50%) caused by direct compression of the superior colliculi. Hearing loss is rare in patients with tumors in this location. The authors report on the case of a 12-year-old boy in whom a malignant pineal germ cell tumor was found together with the unusual occurrence of severe hearing loss due to direct bilateral compression of the inferior colliculi. This condition resolved completely after tumor regression.

Does oxygen deficit to the cerebral blood flow caused by subdural hematoma and/or increased intracranial pressure affect the variations in auditory evoked potentials in white New Zealand rabbits?

The experiment entails surgically placing two subarachnoid bolts and a subdural balloon through the skull of white New Zealand rabbits. One bolt is used to raise the intracranial pressure (ICP) by continuously infusing lactated Ringer's solution (LRS) into the subarachnoid space to maintain the desired level of ICPs, and the second bolt is to monitor the ICP. A subdural balloon is inflated with a known volume of LRS to simulate a subdural hematoma condition. Using various levels of ICP and/or different sizes of balloons, auditory evoked potentials (AEPs) were recorded from a rabbit. The results indicate that a major correlation of changes in AEP peak latencies is due to mechanical forces of a mass (inflated balloon simulating a hematoma) on the brain matter rather than increased ICP. The AEP peak latencies are relatively insensitive to an increase in ICP without the simulated intracranial hematoma. This study provides evidence that oxygen deficit to the cerebral blood flow caused by deformation of certain parts of the brain could be identified using AEPs.

Word deafness after resection of a pineal body tumor in the presence of normal wave latencies of the auditory brain stem response

We studied the case of a 48-year-old woman who had resection of a pineal body tumor in terms of postoperative audiological function. Postoperative magnetic resonance imaging disclosed partial inferior colliculi destruction and medial geniculate body degeneration. A pure tone audiogram revealed only moderate sensorineural hearing loss, but her speech perception was totally impaired. The binaural sound localization function was also impaired. The auditory brain stem response (ABR) showed waves I, III, and V to have normal latencies. The amplitude of wave III was larger than that of wave V. These results support the view that the waves of the ABR are elicited from multiple sources in the auditory brain stem nuclei and tracts. This case suggests a substantial role for the inferior colliculus and medial geniculate body in the processing of speech perception and sound localization.

Defective auditory recognition after small hemorrhage in the inferior colliculi

We report the case of a male patient with a traumatic small hemorrhage partially involving the bilateral inferior colliculi without evidence of a temporal lobe lesion. He was unable to comprehend spoken words although he had intact speech production, reading and writing abilities. Comprehension of environmental sounds was also affected. Among the receptive musical abilities, discrimination of intensity, tone and rhythm were preserved, while recognition of melody was impaired. Audiometry showed normal thresholds for pure tone. Waves I-IV of brainstem auditory evoked potentials were elicited normally, whereas the wave V was elicited with reduced amplitude and prolonged latencies on both sides. The main component of middle latency auditory evoked potentials, which is evoked over both hemispheres by monaural stimulation to either side in normal subjects, was elicited only over the hemisphere contralateral to the ear receiving stimulation. Our patient's auditory findings were similar to those usually found in generalized auditory agnosia. Auditory agnosia is usually considered as a sign of a bitemporal cortical or subcortical disorder, but, in our patient, a brainstem disorder caused a disturbance of auditory recognition similar to auditory agnosia due to a bitemporal lesion. Our patient's auditory findings may belong to the category of a brainstem auditory-processing disorder brought on by a small hemorrhage in the inferior colliculi. In addition, the impairment in our patient implies that, in the neural processing of musical parameters, the decoding of intensity, tone and rhythm is accomplished at the level of inferior colliculus, whereas further cortical processing is necessary for the appropriate recognition of melody.