In fact, it is superior in evaluating the bone structure of the tympanic bulla. However,  it is severely lacking in sensitivity for detection of brainstem lesions, especially with the earlier CT scanners commonly used in veterinary medicine.

CSF analysis is helpful in detecting signs of inflammation resulting from infectious or inflammatory diseases.  This is often done in conjuncture with titers for possible infectious causes, such as Rocky Mountain Spotted Fever. If there is a lesion in the brainstem obstructing CSF flow, the sudden reduction of pressure caudal to the obstruction caused by the spinal tap may facilitate a cerebellar herniation. For this reason, we prefer to evaluate with an MRI before pursuing a spinal tap, if that is at all a possibility.  If imaging is not an option, precautions can be taken to decrease the intracranial pressure with medications, such as mannitol and therapies such as hyperventilation. Prior administration of corticosteroids, while it may be dictated by the animals clinical condition, can reduce the sensitivity of CSF analysis in detecting inflammatory processes.

Brainstem Auditory Evoked Response (BAER) is a technique for evaluating the auditory pathway from the tympanic bulla through the medulla to the caudal colliculus in the midbrain.  While this can localize a disruption in that pathway, it does not reveal the cause. Also, a complete disruption in the pathway will prevent detecting any disruption more centrally (i.e. if an animal is deaf with cochlear degeneration, BAER analysis will be unable to detect a brainstem lesion).

One interesting and often overlooked cause of vestibular disease is Metronidazole (Flagyl) toxicity. While this is usually seen after prolonged administration of high doses, it can be seen at any time and with any strength administration. The signs are those of central vestibular disease, often accompanied by proprioceptive deficits, severe obtundation and muscle tremors. MR imaging, spinal fluid analysis and BAER evaluation will be normal. Diagnosis is made by clinical signs and a history of Metronidazole exposure. Therapy consists of withdrawal of the drug and supportive care over a 5 to 10 day period.  If the diagnosis is strongly suspected, further evaluation with the above tests can be postponed while waiting for the expected improvement. However, close evaluation is necessary in case there is any deterioration, which would imply a cause other than metronidazole.