Abstract
A retrospective clinical study focused on the frequency of rotational vertigo in 63 patients with acute unilateral midbrain strokes involving the vestibular and ocular motor systems. In contrast to unilateral pontomedullary brainstem lesions, rotational vertigo in midbrain lesions occurred with a low frequency (14%) and transient (< 1 day) course. Swaying vertigo or unspecific dizziness (22%) and postural imbalance (31%) were more frequent. Midbrain strokes with transient rotational vertigo manifested with lesions chiefly in the caudal midbrain tegmentum, while manifestations with swaying, unspecific, or no vertigo chiefly occurred in rostral mesencephalic or meso-diencephalic lesions. We hypothesize that these different manifestations can be explained by the distribution of two separate cell systems based on semicircular canal function: the angular head-velocity cells and the head direction cells, both of which code for head rotation. Animal experiments have shown that angular head-velocity cells are located mainly in the lower brainstem up to the midbrain, whereas the head direction cells are found from the midbrain and thalamic level up to cortical regions. Due to the differences in coding, unilateral dysfunction of the angular velocity cell system should result in the sensation of rotation, while unilateral dysfunction of the head direction cell system should result in dizziness and unsteadiness. We simulated the different manifestations of vestibular dysfunction using a mathematical neural network model of the head direction cell system. This model predicted and confirmed our clinical findings that unilateral caudal and rostral brainstem lesions have different effects on vestibular function.
Highlights
Acute unilateral peripheral vestibular syndromes that involve semicircular canal function and are caused by a labyrinthine (Meniere’s disease) or vestibular nerve disorder manifest with rotational vertigo and horizontal-rotatory spontaneous nystagmus
At the time of the first neurological examination upon entering our clinic, only five patients had a transient horizontal spontaneous nystagmus which was gone at day 2
One of these five patients complained about initial rotational vertigo, one about swaying vertigo, and another one about unspecific dizziness
Summary
Acute unilateral peripheral vestibular syndromes that involve semicircular canal function and are caused by a labyrinthine (Meniere’s disease) or vestibular nerve (acute vestibular syndrome, AVS) disorder manifest with rotational vertigo and horizontal-rotatory spontaneous nystagmus. Similar signs and symptoms occur with unilateral vestibular lesions of the root entry zone of the eighth nerve affecting the vestibular fascicle, the vestibular nucleus ( medial and superior parts) [1–7], the nucleus prepositus hypoglossi [7], the cerebellar peduncle [7, 8], and the vestibular cerebellum [8–13]. As these syndromes are elicited by central rather than peripheral vestibular structures, they are called central vestibular pseudoneuritis [14, 15] or, more recently, central acute vestibular syndrome [16].
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