Locomotor dysfunction after surgical lesions in the unilateral vestibular nuclei region in squirrel monkeys

Clinical manifestations of cerebellar infarction according to specific lobular involvement

Lesions in the cerebellum produce various symptoms related to balance and motor coordination. However, the relationship between the exact topographical localization of a lesion and the resulting symptoms is not well understood in humans. In this study, we analyzed 66 consecutive patients with isolated cerebellar infarctions demonstrated on diffusion-weighted magnetic resonance imaging. We identified the involved lobules in these patients using a cross-referencing tool of the picture archiving and communication system, and we investigated the relationships between the sites of the lesions and specific symptoms using χ (2) tests and logistic regression analysis. The most common symptoms in patients with isolated cerebellar infarctions were vertigo (87%) and lateropulsion (82%). Isolated vertigo or lateropulsion without any other symptoms was present in 38% of patients. On the other hand, limb ataxia was a presenting symptom in only 40% of the patients. Lateropulsion, vertigo, and nystagmus were more common in patients with a lesion in the caudal vermis. Logistic regression analysis showed that lesions in the posterior paravermis or nodulus were independently associated with lateropulsion. Lesions in the nodulus were associated with contralateral pulsion, and involvement of the culmen was associated with ipsilateral pulsion and isolated lateropulsion without vertigo. Nystagmus was associated with lesions in the pyramis lobule, while lesions of the anterior paravermis were associated with dysarthria and limb ataxia. Our results showed that the cerebellar lobules are responsible for producing specific symptoms in cerebellar stroke patients.

Instigation and control of treadmill locomotion in high decerebrate cats by stimulation of the hook bundle of Russell in the cerebellum

In high decerebrate cats, pulse train microstimulation of a restricted region of the midline cerebellar white matter produced a generalized increase in postural muscle tone in the neck, trunk, and limb extensor muscles, and air-stepping of all four legs on a stationary surface. On the moving belt of a treadmill, such stimulation produced well coordinated, fore- and hindlimb locomotion as evoked by stimulating the mesencephalic locomotor region (MLR). Microinjection of a neural tracer into the cerebellar locomotion-inducing site resulted in a bilateral retrograde labeling of cells limited to the fastigial nuclei simultaneously with anterograde labeling of fibers projecting bilaterally to the medial pontomedullary reticular formation (mPMRF) the vestibular complex and upper cervical segments. These results have led to our proposition that the effective cerebellar locomotor region (CLR) corresponds to the midline region of the hook bundle of Russell. Passing through this structure are crossed fastigioreticular and fastigiovestibular fibers, together with fastigiospinal fibers. Subsequently, we showed that CLR stimulation resulted in simultaneous short-latency synaptic activation of long-descending reticulospinal and vestibulospinal cells with high synaptic security. Clearly, the fastigial nucleus possesses potential capability to recruit and regulate posture- and locomotor-related subprograms which are distributed within the brainstem and spinal cord by the in-parallel activation of fastigiospinal, fastigioreticular, and fastigiovestibular pathways.Key words: cerebellar locomotor region (CLR), fastigial nucleus, hook bundle of Russell, reticulospinal cell, vestibulospinal cell.

Programmatic vestibular rehabilitation

Although the use of vestibular exercises for patients with persistent vertigo and dysequilibrium has received some attention for many years, organized vestibular rehabilitation therapy programs have only recently been introduced. The benefits of such programs are becoming widely accepted. They typically involve a three-pronged approach: habituation exercises designed to facilitate central nervous system compensation by extinguishing pathologic responses to head motion, postural control exercises, and general conditioning activities. This article will describe the programmatic approach to vestibular rehabilitation, emphasizing selection criteria and reviewing results that may be anticipated when this treatment modality is used in a variety of patient populations.