Welcome! Today is a going to be a busy day! First on your case list is a sick cat so let's dive in. Here is the story:
The cat was presented for a 2-month history of a left head tilt. She was noted to have effusion from the left ear when signs started and was treated with amoxicillin (dose unknown) for 14 days. Clinical improvement was initially noted, but signs relapsed after medications were discontinued and now the owner's are noting a head tilt to the right, with wide head swinging movements (think Stevie Wonder) bilaterally, especially when she first wakes up. She is an indoor only cat, with a history of indoor-outdoor lifestyle over 5 years ago.
Physical Examination
General: T: 99.4 °F/37.4 C Pulse: 180 bpm Resp: 20 breaths/min
Wt.: 3.4 kg BCS: 4/9 MM
Eyes: Corneas are clear, no ocular discharge, normal conjunctiva.
Ears: Mild waxy debris noted in both external ear canals.
Oral cavity: Patient did not allow evaluation
Teeth: Did not evaluate.
Lymph nodes: Normal, no peripheral lymphadenopathy noted.
Heart: No murmurs or arrhythmias, pulses strong and synchronous.
Respiratory system: No nasal discharge, no tracheal sensitivity. Lungs clear on auscultation.
Abdomen: Normal, soft, non-painful, no masses or organomegaly noted.
Musculoskeletal: Not evaluated
Skin and hydration: dry flaky hair, no ectoparasites noted
NEUROLOGIC EXAMINATION
Palpation: No paraspinal pain elicited on palpation
Postural reactions: normal tactile placing and hopping all limbs.
Reflexes: Normal.
Gait: Ambulatory with mild vestibular ataxia and falling left.
Cranial nerve abnormalities: Wide head swinging with an occasional right AND left head tilt, positional rotary nystagmus, mild miosis OS, remainder normal.
Mentation: BAR, occasionally hissing
What is the neuronatomic lesion localization for THIS cat?
This cat has evidence of vestibular disease based on the presence of a head tilt and nystagmus. Cranial nerves 8 are affected by loss of function of the peripheral nerve, brainstem or cerebellum. To differentiate between these three localizations, it is important to evaluate the remaining neurologic examination for clues. Animals with brainstem disease will exhibit a loss of function of the upper motor neurons and ascending proprioceptive pathways which is demonstrated as evidence of ipsilateral hemiparesis and reduced ipsilateral proprioceptive testing. Furthermore, reduced level of alertness (obtunded, coma, stupor) may be noted. If paresis, proprioceptive deficits or reduced mentation are noted the lesion is most likely in the brainstem. Cerebellovestibular disease will manifest with signs of vestibular disease plus evidence of hypermetria, intention tremors and/or truncal sway, suggestive of cerebellar disease. Absence of these findings suggests a peripheral CN 8 neuroanatomic lesion localization. This cat does not have evidence of brainstem or cerebellar disease therefore the signs were localized to the peripheral component of CN 8.
Reduced sympathetic innervation to the eye may occur through damage to the sympathetic pathway. This pathway starts in the hypothalamus, courses caudally through the brainstem, cervical spinal cord, and exits the T1-T3 spinal cord segment and travels cranially in the jugular groove to the cranial cervical ganglion. From the cranial cervical ganglion this pathway runs through the middle ear and along the trigeminal nerve to end in the periorbital muscles, 3rd eyelid and dilator muscle of the iris. Dysfunction anywhere along this pathway will result in miosis in dim light. The lesion in this case is likely in the region of the middle ear due to a lack of neurologic disease noted in the intracranial structures, spinal cord, or along CN 5.
You may be tempted to call this a central lesion because the head tilts BOTH directions but don't! Without signs of hemiparesis, proprioceptive placing deficits or mentation changes a central lesion is unlikely.
Differential diagnoses: The history suggests that we now have a bilateral otitis media/interna but you couldn't rule out a polyp or neoplastic process with a secondary infection.
What did we do?
CBC and serum biochemistry were normal. Thoracic radiographs were unremarkable. The brain MRI showed bilateral debris in the bulla with ring enhancement.
Final diagnosis: Bilateral otitis media/interna. A myringotomy was performed, with ear flushing, cultures and cytology. Unfortunately no growth was noted (this is uncommon!) so marbofloxacin was started and clinical signs improved. She had a left head tilt on presentation for 30 day recheck, and this is expected to be permanent. All other signs of vestibular disease had resolved!
Happy first week of Fall everyone! I hope you and your family had a wonderful summer and look forward to working with you as we dig into what I hope will be a lovely Wisconsin fall.
