Bilateral labyrinthectomy in the cat: motor behaviour and quiet stance parameters

Abstract

The purpose of this study was to examine the effect of bilateral labyrinthectomy on quiet stance in the freely-standing cat. Since loss of the vestibular end organs produces marked deficits in motor behaviour, including ataxia and problems with balance, we hypothesized that labyrinthectomized animals would show impairment in quantitative measures of stance. Stance was quantified in terms of the ground reaction forces under each limb and the tonic electromyographic (EMG) activity of selected muscles. Animals were labyrinthectomized by drilling into the vestibule and removing the vestibular epithelium. Following lesion, animals were able to stand unsupported on the force platform within 2 days. To our surprise, the lesioned animals showed little change in stance parameters from the control, pre-lesion state. Thus, our hypothesis of changes in stance parameters was not supported. There was no change in the distribution of vertical forces under the limbs and no increase in sway, as measured by the area of excursion of the centre of pressure over time. The horizontal plane forces, which were diagonally directed prior to lesion, became more laterally directed and larger in amplitude. The change in direction persisted even after the animals had fully compensated for the lesion, but the force amplitudes returned to control values within 10-12 days. The change in horizontal force direction was similar to that observed in normal animals that were required to stand with their paws closer than preferred in the sagittal plane (unpublished observations). EMG activity changed in some muscles but not others, and usually transiently.(ABSTRACT TRUNCATED AT 250 WORDS)

The Vestibular System: A Newly Identified Regulator of Bone Homeostasis Acting Through the Sympathetic Nervous System

“…Interestingly, some of the vestibular deficits or alterations observed in these conditions disappear with time (phenomenon of compensation), while others, including balance, eye movements in response to head rotations in the dark, navigational abilities, and spatial memory, remain permanently altered [116][117][118][119][120]. In mice, bilateral vestibular sodium arsenilate lesions induce a vestibular syndrome and bone loss after a month, but bone mass returns to normal 3 or 6 months after lesions [85••].…”

Compensation Following Bilateral Vestibular Damage

“…Macpherson and colleagues documented the effects of a bilateral labyrinthectomy on postural stability in cats (Thomson et al, 1991; Inglis and Macpherson, 1995; Stapley et al, 2006; Macpherson et al, 2007). The animals were severely impaired for the first 2 days after lesions, after which they could stand unsupported on a tilt platform and walk in a staggering fashion (Thomson et al, 1991). Within a week, animals could jump to and from a chair, ataxia was profoundly reduced, and locomotion speeds were much faster (Thomson et al, 1991).…”

“…The animals were severely impaired for the first 2 days after lesions, after which they could stand unsupported on a tilt platform and walk in a staggering fashion (Thomson et al, 1991). Within a week, animals could jump to and from a chair, ataxia was profoundly reduced, and locomotion speeds were much faster (Thomson et al, 1991). Although limb muscle responses to linear translations had normal patterning after the loss of vestibular inputs, hypermetria was present for the first 10 days (Inglis and Macpherson, 1995).…”

“…However, some postural deficits were enduring. For example, balance was permanently destabilized when the head was turned (Thomson et al, 1991; Stapley et al, 2006), due to the fact that at peak yaw head velocity the lesioned cats produced an unexpected burst in extensors of the contralateral limbs that thrust the body to the ipsilateral side (Stapley et al, 2006). The magnitude of the counterproductive limb extension was largest during the first few days after lesions, but the response remained present when the experiment was discontinued ∼40 days after the removal of vestibular inputs.…”

“…However, rapid recovery occurs for other consequences of bilateral loss of vestibular inputs, particularly impaired postural stability (Thomson et al, 1991) and inability to maintain stable blood pressure during postural alterations (Jian et al, 1999). It thus is useful to consider the similarities and differences between these responses to gain insights into the process of compensation.…”