Loss of brainstem acoustic evoked potentials with spontaneous breathing in a patient with supratentorial lesion

The loss of brainstem acoustic evoked potentials (BAEP) is considered as a confirmatory test for the diagnosis of brain death in patients with supratentorial lesions. We report a patient with ischemia in the territory of the left middle and anterior cerebral artery, who showed a loss of BAEP waves III-V as a sign of brainstem compression, but maintained spontaneous breathing and EEG activities. We conclude that occasionally BAEP may provide misleading results in the diagnosis of brain death.     

Evidence from auditory nerve and brainstem evoked responses for an organic brain lesion in children with autistic traits

In an attempt to resolve the question as to whether children with autistic traits have an organic nervous system lesion, auditory nerve and brainstem evoked responses were recorded in a group of 15 children with autistic traits. The most obvious results included a longer response latency of the auditory nerve and a longer brainstem transmission time, compared to normal children. Five of the autistic children were found to be profoundly deaf. These results strengthen the theory that an organic lesion of the nervous system can give rise to autistic traits.We wish to acknowledge the cooperation of the following institutions and individuals: Professors Russel and Szabo, Department of Pediatrics, Hadassah University Hospital, Jerusalem; Dr. Perlmutter, Child Mental Health Center, Jerusalem; Dr. Shereshevsky, Child Development Center, Beit Abrahams, Tel Aviv.     

Auditory brainstem evoked responses in brainstem compression due to posterior fossa tumors.

Five patients with unilateral posterior fossa tumors were investigated with Auditory Brainstem Evoked Responses (B.E.R.). The B.E.R., recorded from the ear ipsilateral to the tumor, were consistent with a lesion of the acoustic nerve or the cochlear nuclei in all patients. The contralaterally evoked responses in four patients with large tumors and radiological signs of brainstem compression showed normal latencies and amplitudes of the first three waves, while waves IV and V were definitely abnormal with respect to amplitudes and latencies. (The 4th patient had a normal wave IV and a delayed, small wave V). In one patient with a relatively small acoustic neurinoma the contralateral B.E.R. were normal. It is concluded that the upper pontine and lower midbrain level, presumed sites of generation of wave IV and V of the B.E.R., are more susceptible to brainstem compression due to unilateral posterior fossa tumors, than the lower parts of the brainstem.     

Measuring neck structures in relation to vestibular evoked myogenic potentials.

OBJECTIVE: This study examined whether neck length or thickness influences vestibular evoked myogenic potential (VEMP) responses. METHODS: Twenty healthy children and 20 healthy adults underwent VEMP testing. Two reference points were selected for measuring neck length. Maximum thickness of the subcutaneous tissue and the sternocleidomastoid muscle was measured by ultrasonographic examination. RESULTS: The mean latencies of peaks p13 and n23 in 20 healthy children were significantly earlier than those in healthy adults. Neck length significantly related to p13 latency in children, but not in adults. In contrast, corrected amplitudes did not differ significantly between children and adults. Ultrasonography guided measurement of the subcutaneous thickness in adults associated negatively with raw amplitude, but not with corrected amplitude. CONCLUSIONS: Vestibular evoked myogenic potential latencies correlated positively to neck length in all subjects (children and adults), while raw amplitudes of VEMPs in adults correlated negatively with subcutaneous thickness. No correlation between neck thickness and corrected amplitude was observed. SIGNIFICANCE: Structural differences affecting latencies and raw amplitudes of VEMP responses should be considered when interpreting VEMP parameters.     

Delayed motor and sensory neuropathy in a patient with brainstem encephalitis

Bickerstaff's brainstem encephalitis (BBE), Miller Fisher syndrome (MFS) and Guillain-Barré syndrome (GBS) are thought to be closely related and to form a continuous spectrum. However, chronic polyneuropathy in BBE has not been reported. We report the temporal profile of anti-ganglioside antibody titer in a case of BBE-like brainstem encephalitis complicated with chronic polyneuropathy. A 71-year-old Japanese woman presented with drowsiness and cerebellar ataxia in addition to mild weakness in distal limb muscles. Anti-GalNAc-GD1a IgG and anti-GalNAc-GM1b IgG antibodies were positive in her serum. Brain magnetic resonance imaging revealed high-intensity signals in the midbrain, pons, and middle cerebellar peduncles on T2-weighted images. Central nervous system manifestations improved after immunomodulating therapy that included prednisolone, plasmapheresis and intravenous immunoglobulin. Nevertheless, the distal muscle weakness was exacerbated when the anti-GalNAc-GD1a IgG titer was elevated. Nerve conduction study indicated motor and sensory neuropathy which was developed motor dominant axonal damage. These findings suggest that anti-ganglioside antibodies, including anti-GalNAc-GD1a IgG, may be involved in a common autoimmune mechanism in BBE-like brainstem encephalitis and chronic motor dominant axonal neuropathy. However, the fact that the latter manifestation exacerbated after the improvement of former one possibly indicates different thresholds of neurologic symptoms mediated by anti-ganglioside antibodies in the present patient.     

Short and middle latency vestibular evoked responses to acceleration in man.

We have succeeded in recording short and middle latency vestibular evoked responses in human subjects. The head was held rigidly in a special, patented head holder, constructed individually for each subject, which gripped the teeth of the upper jaw. The stimulus consisted of 2/sec steps of angular acceleration impulses produced by a special motor with intensities of about 10,000 degrees/sec 2 and with a rise time of 1-2 msec. The electrical activity was recorded as the potential difference between special forehead and mastoid electrodes having a large, secure contact area with the skin. The activity was digitally filtered and averaged in 2 separate channels by means of a Microshev 2000 evoked response system. The short latency responses, with peaks at about 3.5 msec (forehead positive), 6.0 msec (forehead negative) and 8.4 msec (forehead positive; bandpass: 200-2000 Hz; average of 1024 trials), had amplitudes of about 0.5 microV. The middle latency responses had peaks at about 8.8 msec (forehead positive), 18.8 msec (forehead negative) and 26.8 msec (forehead positive; 30-300 Hz; N = 128 trials), with larger amplitudes (about 15 microV). These responses were consistently recorded in the same subject at different times and were similar in different normal subjects. Strenuous control experiments were conducted in order to ensure that these responses are not artefacts due to the movement of conducting media (head, electrodes and leads) in the electromagnetic field of the motor and are elicited by activation of normal labyrinths.(ABSTRACT TRUNCATED AT 250 WORDS)     

前庭阵发症脑干听觉诱发电位的特点

目的探讨前庭阵发症(VP)脑干听觉诱发电位(BAEP)的特点。方法对51例VP患者的BAEP结果进行回顾性分析。结果 BAEP异常者40例,异常率为78.4%。与Ⅰ-Ⅲ波峰间期正常的患者相比,Ⅰ-Ⅲ波峰间期延长的患者男性比例高(χ2=4.763,P=0.029),病程显著延长(t=2.469,P=0.021),而平均年龄差异无统计学意义。与Ⅲ-Ⅴ波峰间期正常的患者比较,Ⅲ-Ⅴ波峰间期延长的患者男性比例、平均病程、平均年龄差异均无统计学意义。与Ⅰ-Ⅲ波峰间期耳间差正常的患者比较,Ⅰ-Ⅲ波峰间期耳间差延长的患者病程相对较长(P=0.055),男性有增多趋势(P=0.058),但差异无统计学意义。结论 VP患者BAEP异常以Ⅰ-Ⅲ波峰间期延长为主,且以男性更多见。病程越长,蜗神经越易受累。     

Observations upon the evoked responses to natural vestibular stimulation

Repetitive rotational stimuli simulating natural head movements have been applied to the study of the vestibular evoked response in normal subjects and 12 patients with complete loss of vestibular function. Special precautions were taken to eliminate all possible sources of artefacts, in particular, all eye movements were restrained by requiring the subject to fixate upon a target light attached to the rotating chair throughout the course of the test. With a stimulus of 2 sec duration the typical response took the form of a slow negative wave with a mean peak amplitude of approximately 24 microV and maximally recorded from the vertex. It was characteristically absent in the patient group. Occasionally, both in normal subjects and patients it was preceded by a long latency complex thought to be non-vestibular in origin. Tests carried out both in total darkness and in the light show a statistically significant increase in the potential in the latter condition indicating an influence of the optokinetic effect exerted by the visual surround. Further studies have explored the phase changes brought about by varying the amplitude and duration of the stimulus. These have revealed certain parallels in the results of recent animal experimental studies.     

Brainstem reflexes and brainstem auditory evoked responses in Huntington''s chorea.

Blink reflex, corneal reflex, jaw reflex, exteroceptive suppression in masseter muscles and brainstem auditory evoked potentials were measured in 20 patients with Huntington's chorea and 12 controls. A significantly increased latency of the second component of the homolateral and heterolateral blink reflex was found in the patient group as compared with the controls. The other investigations revealed no significant differences between patients and controls except for some facilitation of the jaw reflex in the patient group. Increase of second component latency of the blink reflex in the presence of normal corneal reflexes is suggestive of functional impulse conduction disturbance in the lower brainstem. It is discussed whether in Huntington's chorea this is to be attributed to alterations of cortical or striatal influence or to local brainstem abnormalities.     

Rhythmic involuntary movement of the neck in a patient with brainstem encephalitis]

A 36-year-old Japanese woman was admitted to our hospital, because of facial palsy, ophthalmoplegia, cerebellar ataxia, and rhythmic myoclonus of the neck. About a few weeks before admission, she developed symptoms of common cold and general fatigue. Her laboratory data were unremarkable, and her CSF was normal. Serum levels of antibodies to gangliosides were within normal limits. Her MRIs of the brain and neck were normal. Both somatosensory evoked cortical potential study and auditory evoked brainstem response study were normal. She was diagnosed as postinfectious brainstem encephalitis, and the administration of corticosteroid was started. After the treatment, her symptoms improved. To our knowledge, it is rare to see myoclonus to the neck without palatal tremor in patients with brainstem encephalitis.     

Ocular vestibular evoked myogenic potentials to head tap and cervical vestibular evoked myogenic potentials to air-conducted sounds in isolated internuclear ophthalmoplegia

ObjectiveThe central pathways responsible for ocular vestibular evoked myogenic potentials (VEMPs) to forehead tapping remain to be determined. This study aimed to determine whether the medial longitudinal fasciculus (MLF) carries the signals for ocular VEMPs (oVEMPs) in response to this mode of stimulation.MethodsTwelve patients with isolated unilateral internuclear ophthalmoplegia (INO) due to brainstem infarction underwent evaluation of the ocular tilt reaction (ocular torsion and skew deviation), tilt of the subjective visual vertical (SVV), cervical VEMPs (cVEMPs) in response to tone burst sound, and oVEMPs induced by tapping the forehead.ResultsEight (67%) patients showed abnormal oVEMPs that included no wave formation (n = 4) and decreased amplitude (n = 3) in the lesion side, and bilaterally absent responses in the remaining patient. Furthermore, the patients showed diminished oVEMPs responses in the lesion side compared with normal side (6.0 ± 5.6 vs. 11.7 ± 5.5 μV, paired t-test, p = 0.001) and increased IAD_amp(%) of the oVEMPs compared with normal controls (43.6 ± 41.2 vs. 9.1 ± 6.2, t-test, p = 0.018). In contrast, cVEMPs were abnormal in only three (25%) patients, decreased (n = 2) or no response in the lesion side. Eleven (92%) patients showed contraversive ocular tilt reaction or SVV tilt.ConclusionPatients with INO frequently show impaired formation of ipsilesional oVEMPs in response to forehead tapping. The occasional abnormality and decreased amplitude of ipsilesional cVEMPs also suggest a modulatory pathway for the inhibitory sacculocollic reflex descending in the MLF.SignificanceThis study suggests that the MLF contains the fibers for the otolith-ocular reflex from the contralateral ear.     

Ocular vestibular evoked myogenic potentials induced by air-conducted sound in patients with acute brainstem lesions

ObjectiveThe ocular vestibular-evoked myogenic potential (oVEMP), a recently documented otolith-ocular reflex, is considered to reflect the central projections of the primary otolithic afferent fibers to the oculomotor nuclei. The aim of our study is to define air-conducted sound oVEMP abnormality in patients with acute brainstem lesions and to determine the brainstem structures involved in the generation of oVEMPs.MethodsIn response to air-conducted tone burst sounds (ACS), oVEMP was measured in 52 patients with acute brainstem lesions. Individualized brainstem lesions were analyzed by means of MRI-based voxel-wise lesion-behavior mapping, and the probabilistic lesion maps were constructed.ResultsMore than half (n = 28, 53.8%) of the patients with acute brainstem lesions showed abnormal oVEMP in response to ACS. The majority of patients with abnormal oVEMPs had lesions in the dorsomedial brainstem that contains the medial longitudinal fasciculus (MLF), the crossed ventral tegmental tract (CVTT), and the oculomotor nuclei and nerves.ConclusionMLF, CVTT, and the oculomotor nuclei and nerves appear to be responsible for otolith-ocular responses in the brainstem.SignificanceComplemented to cervical VEMP for the uncrossed otolith-spinal function, oVEMP to ACS may be applied to evaluate the crossed otolith-ocular function in central vestibulopathies.     

Sound movement detection deficit due to a brainstem lesion.

Auditory psychophysical testing was carried out on a patient with a central pontine lesion involving the trapezoid body, who presented with a deficit in sound localisation and sound movement detection. A deficit in the analysis of time and intensity differences between the ears was found, which would explain the deficit in detection of sound movement. The impaired detection of sound movement, due to a lesion interfering with convergence of auditory information at the superior olive, suggests this structure to be critical for human sound movement analysis.     

Auditory brainstem evoked responses (ABER) in children with autistic behaviour

Rabbits were tested binocularly and with each eye separately, in pattern discriminations sensitive to the removal of the visual cortex opposite the exposed eye before and after the middle cerebral artery was unilaterally coagulated. Following surgery, the rabbits were not impaired in performing the discriminations with either eye; nor were any pathological changes found in the hemisphere in which surgery was performed. These findings imply that deficits in performing tasks dependent on the integrity of the visual cortical areas in rabbits may require interruption of the posterior and middle cerebral arteries, both of which supply the visual cortical areas.     

Ocular tilt reaction due to an upper brainstem lesion: Paroxysmal skew deviation,torsion, and oscillation of the eyes with head tilt

A patient with a focal brainstem abscess in the region of the zona incerta developed a chronic oculocephalic dyskinesia in which paraoxysmal tonic skew deviation and torsion of the eyes were coupled with ocular oscillations and head tilt.     

Recording of electrically evoked auditory brainstem responses (E-ABR) with an integrated stimulus generator in Matlab

Electrical auditory brainstem responses (E-ABRs) of subjects with cochlear implants are used for monitoring the physiologic responses of early signal processing of the auditory system. Additionally, E-ABR measurements allow the diagnosis of retro-cochlear diseases. Therefore, E-ABR should be available in every cochlear implant center as a diagnostic tool. In this paper, we introduce a low-cost setup designed to perform an E-ABR as well as a conventional ABR for research purposes. The distributable form was developed with Matlab and the Matlab Compiler (The Mathworks Inc.). For the ABR, only a PC with a soundcard, conventional system headphones, and an EEG pre-amplifier are necessary; for E-ABR, in addition, an interface to the cochlea implant is required. For our purposes, we implemented an interface for the Combi 40+/Pulsar implant (MED-EL, Innsbruck).