Effects of lateral ampullary nerve section in squirrel monkeys

Are vestibular sensory cells preserved after destruction of Scarpa's ganglion? A study based on metastatic tumors of temporal bone

OBJECTIVE

The contribution of nerve fibers to the maintenance of vestibular sensory cells is a controversial issue in previous studies using animals and has not yet been studied in humans. The authors investigated this issue by observing vestibular end organs in the temporal bone of three patients in whom the internal auditory canal was infiltrated with tumor cells, and Scarpa's ganglion cells showed complete degeneration.

STUDY DESIGN

Retrospective case review.

SETTING

University Hospital, Department of Otolaryngology.

PATIENTS

Three patients with malignant metastatic temporal bone tumors.

INTERVENTION

We investigated the preservative state of vestibular sensory hair cells with the Scalpa's ganglion was destructed.

MAIN OUTCOME MEASURES

Maintenances of vestibular sensory hair cells.

RESULTS

We found that sensory cells were intact despite the severe destruction of Scarpa's ganglion cells in two of the patients.

CONCLUSION

The findings suggest that human vestibular sensory cells can be maintained for an indefinite period after denervation.

Effects of caloric vestibular stimulation on head and trunk movements during walking

The effects of vestibular stimulation on head and trunk movements were investigated during human walking (4.0 km/h). Vestibular stimulation was produced by irrigating an external auditory meatus with 4 degrees C ice water for 10 s. Using a 3-D motion analysis system, the linear (medial/lateral and vertical) translations and angular (yaw, pitch and roll) rotations were determined at the head, thorax, pelvis, knee, and foot. After caloric stimulation, waking trajectory deviated toward the stimulated side during dizziness. In addition, the amplitude of medial/lateral (M/L) linear translation and yaw rotation were significantly increased by caloric stimulation, especially at the head and thorax, whereas changes in vertical translation and pitch and roll rotations were not significant. The compensatory coordination (i.e., the yaw rotation to oppose the M/L linear translation) of the head was precisely maintained both before and after caloric stimulations, but it was decreased at the thorax and pelvis after stimulation. Our results suggested that vestibular sensory information, probably via the horizontal semicircular canals, contributes predominantly to the regulation of dynamic head and trunk movements in the M/L direction.

The squirrel monkey stabilimetry

In order to characterize postural ataxia associated with peripheral vestibular lesions, we have developed a T-perch recording system suitable for squirrel monkeys (tree-living primates). This system includes strain gauges for detecting movement of the vertical shaft in the directions of anterior-posterior and left-right. Simultaneously we recorded electroencephalogram (EEG), vertical eye movement, electrocardiogram (ECG) and respiration (by pneumography). Representative Dynographic records (obtained during sleep) after unilateral and bilateral (two-staged) labyrinthectomy showed the frequent occurrence of phasic body movements: slow deviations to the lesion side and the frontward and subsequent quick rightings which occurred almost synchronously with the sleep becoming shallow (judged by EEG).

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

The present experimental results in squirrel monkeys indicated that the performance of psycho-physically advanced locomotor task (squirrel monkey rail test) was severely impaired after the placement of the medium to relatively large surgical lesions in the unilateral vestibular nuclei area, and therefore, confirmed that this brain-stem structure is essential for the signal relay and/or input coordination. The severest locomotor disability was found 10-14 days after the surgery; thereafter, squirrel monkeys showed very gradual and only limited degree of performance recovery. The post-ablative performance levels were no better than 1/5 of their pre-ablative performance levels.

Effect of different vestibular lesions upon body equilibrium function in squirrel monkeys

By utilizing the squirrel monkey rail test, postoperative compensation status after unilateral saccular macula destruction, unilateral utricular nerve section and unilateral lateral ampullary nerve section, were studied in a quantitative fashion and the results were statistically compared. First, it was confirmed that the preoperative random assignments of subjects were evenly distributed among different experimental categories and therefore inter-categoric statistical comparisons of postoperative status were valid. Minimal effect after the unilateral saccular macula ablation toward the maintenance of body equilibrium was reconfirmed. The utricular input is probably the most important for the maintenance of body equilibrium function, inasmuch as slightly less equilibrium disturbance was found after unilateral lateral ampullary nerve cut even though the difference was not significant.

Experimental studies on the nerve--sensory cell relationship during degeneration and regeneration in ampullar nerves of the frog labyrinth

The degeneration and regeneration of afferent and efferent nerves to the crista ampullaris in the frog were studied after transsection of the ampullar nerves. In some experiments one or both rostral ampullar nerves were simply divided and left in place. In other experiments the ampullar nerves to the horizontal and to the anterior vertical crista were divided and the branch to the former was brought into contact with the distal stump of the anterior vertical ampullar nerve. Sensory cells in the labyrinth survived total denervation for 1-2 weeks without regular signs of ultrastructural damage. The afferent synaptic structures in these cells were often preserved in the denervated stage. The afferent nerve fibres degenerated earlier than the efferent ones. Both type of fibres reinnervated the vestibular epithelium after division of the ampullar nerve. The fibres from a horizontal ampullar nerve could reinnervate a denervated anterior vertical crista, resulting in misdirected reflexes. About 40 days after division both function and morphological organization had been restored to normal.