Vestibular syndrome: What's causing the head tilt and other neurologic signs? - Veterinary Medicine
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Vestibular syndrome: What's causing the head tilt and other neurologic signs?


VETERINARY MEDICINE



Dr. Helena Rylander
Vestibular syndrome is not a disease per se but a conglomerate of neurologic signs due to a dysfunction in the vestibular system, either peripheral or central.

Based on neurologic examination findings, a vestibular lesion can be localized to the peripheral or central vestibular system.1 This distinction is important since the differential diagnoses, work-up, treatment, and prognosis in patients with peripheral vestibular dysfunction are different from those in patients with central vestibular dysfunction.

Here's how to first determine whether a vestibular problem stems from the inner ear or the brain and then how to pinpoint the underlying cause and administer appropriate treatment.

PERIPHERAL VS. CENTRAL VESTIBULAR ANATOMY

The vestibular system maintains balance and coordinates the position of the head, eyes, neck, and limbs in space.


1. A CT scan of the inner ear in the petrous temporal bone (red circles).
The peripheral vestibular system comprises three semicircular canals, the utricle and saccule in each inner ear, and the vestibulocochlear nerve (cranial nerve [CN] VIII).2 The inner ear is located in the petrous temporal bone (Figure 1).

The central vestibular system comprises eight vestibular nuclei in the brainstem (four on each side), two caudal cerebellar peduncles, and the flocculonodular lobe of the cerebellum (Figure 2).1


2. MRI of the central vestibular system’s location in the brainstem and cerebellum (red circle).
The vestibular nuclei then project to the cerebellum, contralateral vestibular nuclei, reticular formation of the brainstem, the spinal cord, the cerebrum, and the extraocular muscles via the medial longitudinal fasciculus and CN III, IV, and VI.1

SIGNALMENT AND HISTORY CLUES

Although rare, puppies may have a congenital peripheral or central vestibular disorder.3,4 Vestibular dysfunction due to neoplasia is more common in older dogs, although a primitive neuroectodermal tumor may cause vestibular signs in a young dog.

Vestibular signs are often acute in onset regardless of the lesion's location. Metronidazole toxicosis as a cause of vestibular signs may be supported by a history of metronidazole treatment. Dosages as low as 67.3 mg/kg/day in a dog and 58 mg/kg/day in a cat have been documented to cause vestibular signs.5,6 I have diagnosed metronidazole toxicosis in a dog that received 40 mg/kg/day. A recent ear infection may precede peripheral vestibular dysfunction. A systemic disease such as hypothyroidism or hyperadrenocorticism—possibly uncovered through a physical examination and laboratory testing—may cause peripheral or central vestibular dysfunction.


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Source: VETERINARY MEDICINE,
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