I read an interesting article recently about positioning head tilts in cats with hypokalemia myopathy (https://doi.org/10.1177/1098612X231175761) This isn't likely to be something you encounter often in practice, but I hope you will also find it an intesting read nontheless.
Hypokalemic myopathies are common in cats and often result in signs of weakness including cervical ventroflexion and/or tetraparesis. We can see hypokalemia secondary to renal disease, hyperthyroidism, dietary insufficency, chronic vomiting/diarrhea, and other metabolic causes. The subsequent myopathy occurs due to overpolarization of the muscle sarcolemma resting membrane potential making it resistant to depolarisation. Without depolarization, there is no muscle contraction and we see clinical weakness.
When the head is turned, the cerebellum (specifically the nodulus and uvula) receive input from the vestibular nuclei, who in turn receive sensory information from the stretch receptors in the cervical muscles, on the whereabouts of the head and neck. This allows the cerebellum to modify the head position so that the head remains paralell to the ground as it is turned. With positioning head tilts, the head tilts to the opposite direction that the head is turning. When looking straight, no head tilt is observed. When turning right, the head tilts slightly to the left, for example.
This article described 14 cats who had a positioning head tilt obseved on neurologic examintation AND had concurrent hypokalemia. One cat had an MRI and no cerebellar lesions were noted. Does that mean the others didn't? No, of course not. However, when the potassium was normalized the positional head tilt resolved. This would suggest cause and effect but isn't definative. The authors supposed that the muscle firing in the spindle fibers (the very small muscles located in the bigger muscles that convert stretch to neuronal impulse for sensory information) weren't able to depolarize appropriately. This lack of depolarization resulted in an absence of information about the whereabouts of the cervcial muscles (and those attached to the head, specifically) and didn't allow the cerebellum to modify head posture when turning. Pretty cool, huh? Although this is just a therory, I personally think it is pretty slick and clever.
Take home message:
What do you do with a positioning head tilt in a cat? Look for hypokalemia and if identified, address it!
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Have a great week. I hope you enjoyed this little TidBit as much as I did. I look forward to working with you soon!