The vestibular system is a series of nerves, nuclei, portions of the brain, and organs of the inner ear that control the body’s sense of orientation and balance, helping the animal to understand movement. This system allows the animal to compensate for both their own movement and outside forces such as gravity, providing the ability to detect and respond to a stimulus. The vestibular system also works in conjunction with input from the eyes and proprioception from muscles, skin, and joints allowing the body to integrate sensory input and maintain balance. (Watson, etc.) To maintain normal balance, the three canals within the inner ear are filled with fluid and sensory hairs, both of which respond to the orientation of the head. Each tube is positioned at a 90 degree angle to the next and is more sensitive to movements that lie on its specific plane. As the fluid moves within the tubules, the hairs are stimulated and send nerve impulses to the brain. These never impulses are read and a message is sent to the body to respond, maintaining balance.
Diseases that affect the vestibular system can be separated into two categories: peripheral and central. While both categories of diseases result in a change of the animal’s balance, peripheral vestibular disease affects the quality of the message the animal is then sending to the brain. These conditions are more common, affecting the organs and nerves of the inner ear. Causes of peripheral vestibular diseases include hypothyroidism, otitis interna, idiopathic conditions, neoplasia of the inner or middle ear, and trauma. In most feline cases, however, the common cause in aged patients is feline idiopathic vestibular disease. Though both categories may lead to a loss in balance, varying signs and onset can help with diagnosis. Conducting a proper physical exam and thorough history is the first step to a working diagnosis. Signs include: head tilt, vestibular ataxia, circling, falling down, rolling, nystagmus, strabismus, nausea, vomiting, ptyalism, Horner’s syndrome, facial nerve paralysis, postural reaction deficits, change in mentation.
Diagnostic Testing can include visualizing the ear drum, radiographs, CT, and MRI to assess the overall health of the tympanic bulla and middle/inner ear. Blood testing allows detection of any hormonal imbalances such as hypothyroidism and hyperadrenocorticism. Assessing a sample from either the inner ear or fluid from the spinal cord for infection or inflammatory causes. If the patient is suffering from otitis media or otitis interna, the ear should be examined for mites, foreign debris, and a culture should be taken.
The treatment necessary for vestibular disease is dependent on the cause, but alleviation of symptoms using secondary treatment while the primary disease is treated can make the patient more comfortable. Antihistamines such as meclizine, dimenhydrinate, or diphenhydramine can be used to treat the nausea and dizziness, allowing the animal to feel more comfortable and adept to eating/drinking. Antiemetics such as maropitant citrate or metoclopramide can be used to alleviate the feeling of needing to vomit. (Birchall, 2017)
Each form of treatment will accompany aggressive nursing care, as these animals may have difficulty with mentation or be fully non-ambulatory. They may require help walking, using a sling to stabilize them or to be carried. A calm, quiet area with a large amount of padding and traction will make motility easier and safer for our patient. Eventually, learning a sense of compensation for the current balance issue will help them re-gain some motility. IVF will aid with dehydration, as many will not eat or drink due to nausea or being physically unable to hold themselves long enough to do so. Feeding via orogastric or nasogastric tubes may be considered with patients who show no improvement/ show no incentive to eat.