Lower Brainstem Lesions Research Articles

Thalamocortical network: a core structure for integrative multimodal vestibular functions.

To apply the concept of nonreflexive sensorimotor and cognitive vestibular functions and disturbances to the current view of separate right and left thalamocortical systems. The neuronal modules for sensorimotor and cognitive functions are organized in so-called provincial hubs with intracommunity connections that interact task-dependently via connector hubs. Thalamic subnuclei may serve not only as provincial hubs but also in higher order nuclei as connector hubs. Thus, in addition to its function as a cortical relay station of sensory input, the human thalamus can be seen as an integrative hub for brain networks of higher multisensory vestibular function. Imaging studies on the functional connectivity have revealed a dominance of the right side in right-handers at the upper brainstem and thalamus. A connectivity-based parcellation study has confirmed the asymmetrical organization (i.e., cortical dominance) of the parieto-insular vestibular cortex, an area surrounded by other vestibular cortical areas with symmetrical (nondominant) organization. Notably, imaging techniques have shown that there are no crossings of the vestibular pathways in between the thalamic nuclei complexes. Central vestibular syndromes caused by lesions within the thalamocortical network rarely manifest with rotational vertigo. This can be explained and mathematically simulated by the specific coding of unilateral vestibular dysfunction within different cell systems, the angular velocity cell system (rotational vertigo in lower brainstem lesions) in contrast to the head direction cell system (directional disorientation and swaying vertigo in thalamocortical lesions). The structural and functional separation of the two thalamic nuclei complexes allowed a lateralization of the right and left hemispheric functions to develop. Furthermore, it made possible the simultaneous performance of sensorimotor and cognitive tasks, which require different spatial reference systems in opposite hemispheres, for example, egocentric manipulation of objects (handedness) and allocentric orientation of the self in the environment by the multisensory vestibular system.

The somatosensory blink reflex in upper and lower brainstem lesions

The brainstem pathways that mediate the somatosensory blink reflex (SBR) are not completely understood. We hypothesized that the circuits of the SBR might be affected separately from those of the trigeminal blink reflex (TBR). We examined 7 patients with mesencephalic lesions and 8 patients with medullary lesions. The SBR was elicited by median nerve stimulation. The TBR was elicited by supraorbital nerve stimulation. In patients with upper brainstem lesions, the TBR was normal, whereas the SBR was generally abnormal. The SBR was either absent or small and was significantly delayed with respect to control subjects. The opposite was the rule in patients with lower brainstem lesions who had delayed or absent TBR and no abnormal findings in the SBR. The SBR is mediated through circuits in the upper brainstem. Study of the SBR can be helpful in the neurophysiological assessment of patients with mesencephalic lesions.

Evaluation of brainstem function in patients with spasmodic dysphonia using vestibular evoked myogenic potentials and auditory brainstem responses

Conclusion. The vestibular area is closer than the auditory region to nucleus ambiguus. If a ‘shared’ lesion involves regions of adjacent nuclei of the brainstem in patients with spasmodic dysphonia then vestibular area involvement is more possible than that of the auditory region. Objectives. The authors hypothesize that lower brainstem lesions and involvement of descending pathways of the spinal tract may be the site of lesion in patients with spasmodic dysphonia. Patients and methods. Ten patients with spasmodic dysphonia were tested using the auditory brainstem response (ABR) and vestibular evoked myogenic potentials (VEMPs). Results. No ABR abnormalities were found in right ears. Results of ABR on the left ear showed that one patient had abnormal ABR. This patient had severe sensorineural hearing loss on the left side. VEMPs displayed normal response in two patients bilaterally. First positive (p13) and second negative (n23) waves of VEMP could not be recorded in three cases unilaterally and in five patients bilaterally.

Clinical Study of Vestibular-evoked Myogenic Potentials and Auditory Brainstem Responses in Patients with Brainstem Lesions

A total of 13 patients, who were diagnosed with localized brainstem lesions using MRI, were investigated. The diagnoses were multiple sclerosis in five patients, brainstem hemorrhage in three patients, pontomedullary infarction in one patient and Wallenberg's syndrome in four patients. In addition, 42 ears of 21 normal adult volunteers were also examined. In a patient with upper brainstem lesions mainly affecting the midbrain, the auditory brainstem response (ABR) was abnormal but the vestibular-evoked myogenic potential (VEMP) was normal. In four patients with middle brainstem lesions which mainly affected the pons, both ABR and VEMP were abnormal. In five patients with lower brainstem lesions which mainly affected the medulla, the ABR was normal but the VEMP was abnormal. In those patients with middle-to-lower brainstem lesions, a disappearance of VEMP reactions, delay of the positive-negative (PN) wave, increase in PN interpeak latency and decrease in PN amplitude on the affected side were confirmed. In conclusion, the VEMP test comprises a useful new diagnostic method for identifying lower brainstem lesions.

NEURO‐OPHTHALMOLOGICAL FINDINGS IN RELATION TO CNS LESIONS IN PATIENTS WITH MYELOMENINCOCELE

Twenty-eight patients (14 male, 14 female; aged four to 34 years) with myelomeningocele were studied. Magnetic resonance imaging was used to determine the correlation between disturbances of ocular motility and the degree of hydrocephalus, tectal plate deformity and dislocation of the cerebellum and medulla oblongata. All patients had Chiari malformations. Strabismus and spontaneous nystagmus were strongly related mainly to the degree of hydrocephalus and to some extent to the amount of lower brainstem deformities. Ocular motility defects with regard to oblique muscle functions and horizontal and vertical gaze and saccadic control often correlated with lower brainstem lesions. Convergence defects correlated with deformities of the upper brainstem. However, these correlations were not valid in the individual patient; some had no strabismus and normal ocular motility, in spite of advanced hydrocephalus and Chiari malformations.

Central post-stroke pain — somatosensory evoked potentials in relation to location of the lesion and sensory signs

Somatosensory evoked potentials (SEPs) were studied in 27 patients with central post-stroke pain and in 19 controls. A scoring system for SEP was used, in which increasing abnormalities rendered increasing scores. SEPs evoked by electrical stimulation of the median and tibial nerves were compared to perception thresholds for touch, vibration, innocuous and noxious temperature. All patients had reduced temperature sensibility, while the threshold for touch and vibration was abnormal in only 52% and 41%, respectively. Decreased touch and vibration sensibility had a high correlation with high SEP scores, while no correlation was found between reduced temperature sensibility and SEP. The patients with thalamic lesions had the most severely affected SEPs, the ones with lower brain-stem lesions were the least affected. The results support the notion that the SEP is dependent on the lemniscal pathways and that lesions of the spinothalamic pathways are crucial for the development of CPS.

Stability and tremor in the fingers associated with cerebellar hemisphere and cerebellar tract lesions in man.

Stability and tremor in the fingers were assessed by a new technique in patients with unilateral cerebellar syndromes. In 11 patients with unilateral cerebellar hemisphere lesions tremor was observed with either clear tremor at 5-7 Hz or prolongation of the tremor profile out to 11 Hz. In 10 patients with unilateral cerebellar lesions associated with ipsilateral past-pointing there was an asymmetry in finger stability. Compared with normal subjects there was a significant decrease in stability contralateral to the lesion, while the ipsilateral side's stability was not different from normal. In patients with high brain stem lesions at the level of cranial nerves VII and above, tremor had frequencies of 5-7 Hz. In those with lower brain stem lesions, often with long tract signs as well, the frequencies of tremor were faster, 8-11 Hz, which may reflect damage to cerebellar inflow tracts. A broad if not specific correlation was found between clinical condition, site of lesion and finger stability and tremor.

CT-Guided Stereotactic Biopsies of Lesions in the Medulla and a Case of Leigh's Disease

CT-guided stereotactic biopsy of lower brain stem lesions in 7 consecutive cases is discussed. A frontal transincisural approach was used. Five patients had astrocytomas histologically. The single patient who had undergone empirical radiation therapy prior to tissue diagnosis revealed only necrosis. One patient was found to have pathology suggestive of Leigh's disease. This patient was not radiated and is the first alive adult to have this diagnosis confirmed. Although controversy still exists in the management of brain stem lesions, we intend to demonstrate the value of tissue diagnosis in the management of such lesions.

CT-Guided Stereotactic Biopsy of Lower Brain Stem Lesions

CT-Guided Stereotactic Biopsy of Lower Brain Stem Lesions

Differential diagnosis of central vestibular disorders by combined tests with perrotatory ocular fixation and auditory brain stem response.

The purpose of this study is to investigate the diagnostic value of using the damped pendular rotation test (DPRT) (1) with an ocular fixation (ocular fixation test, i.e. OFT), and (2) in the dark with the eyes open, jointly with auditory brain stem response (ABR) audiometry. Impairment of ocular fixation was found in patients with either brain stem lesions, cerebellar lesions, or cerebellopontine angle tumors. A collective evaluation of the findings of OFT with those of ABR audiometry has suggested the possibility of differentiating upper brain stem lesions from lower brain stem lesions, tumors of the IVth ventricle, and cerebellar tumors. However, differentiating IVth ventricle lesions from tumors involving the cerebellar vermis extending into the IVth ventricle by this battery of tests was somewhat limited.

13. Clinico-Pathological Investigation on the Urinary Disturbance and Lower Brain Stem Lesions

13. Clinico-Pathological Investigation on the Urinary Disturbance and Lower Brain Stem Lesions