Time for a Tongue Twister!

Signalment: 12 year old MC Mixed breed dog, 45 kg
History: 1 month history of change in bark, with a 1-2 week history of difficulty eating and drinking. The owners also identified difficulty walking in the last few days and a decrease in the dog's interaction with them.
Physical Examination: Grade II/VI left heart murmur, previously noted and not progressed. The remainder of the exam was unremarkable.

Neurologic Examination

Mentation: Mildly obtunded. The pet interacted when asked, but otherwise seemed content to stare at the floor.
Cranial nerves: Decreased to absent gag reflex, tongue atrophy (see the photo above), all remaining cranial nerves were normal.
Gait: Ambulatory mild proprioceptive ataxia in all four legs
Reflexes: Normal spinal reflexes including c. trunci and perineal.
Palpation: Non painful spinal palpation however pain elicited with cervical ventroflexion
Postural reactions: absent right thoracic and right pelvic limb paw replacement test, normal left paw replacement thoracic and pelvic.

Neuroanatomic Lesion Localization?? To do this, we need to break it down and identify all of the possible anatomic localizations each neurologic deficit could be noted. Unfortunately the table does not copy to this blog very well so please email me or join our TidBit Tuesday mailing list to get all of the details.
What I did was list all of the possible locations that the affected deficit might involve and then narrowed down the lesion localization two ways:

1. Find the common denominator. In this case, the medulla. OR

2. Find the cranial nerve(s) affected and determine if the pet also has: a) abnormal mentation, b) hemiparesis ipsilateral to the affected cranial nerve or c) paw replacement deficits ipsilateral to the affected cranial nerve. If they do, it is central. If not, it is a likely a peripheral neuropathy.

Neuroanatomic Lesion Localization: Medulla, right side.

Differential Diagnoses: Neoplasia, meningoencephalitis (infectious or inflammatory)

Case Conclusion

This dog had normal CBC, serum biochemistry, UA, chest radiographs and abdominal ultrasound. Brain MRI identified a discrete contrast enhancing extra-axial mass in the right caudal fossa affecting the right side of the medulla. This finding was most consistent with a meningioma. A spinal tap was not performed due to the proximity of the mass to the cerebellomedullary cistern. Based on the working diagnosis surgical decompression, radiation therapy or supportive care were discussed with the owners and they elected supportive care.

You may recognize this case if you have been a loyal TidBit Tuesday reader. This was repeated from February 2020 because I felt like it was a good time to review cranial nerve lesion localization with a very interesting cranial nerve deficit. Thanks for reading (again)!

I hope you have a great week!

Idiopathic Facial Nerve Paralysis

Idiopathic Facial Nerve Paralysis

I thought we'd continue our theme from last week about peripheral neuropathies and talk about a neuropathy that we all (I think) see fairly regularly: Idiopathic facial nerve paralysis.

What is it?
Idiopathic facial nerve paralysis (IFNP) happens for, ahem, unknown reasons. There is some type of synaptic block that, as of now, has an unknown cause. The facial nerve is a motor nerve that starts in the medulla (brainstem), courses through the skull and bulla on it's way to the face. Other causes of facial nerve paralysis such as hypothyroidism, neoplasia, otitis media, polyps, and rarely neuritis. Remember: you must localize the lesion to the peripheral CN 7 to include IFNP on your list of differential diagnoses!

What does it look like?
The facial nerve innervates the muscles of facial expression in dogs and cats as well as providing innervation to the lacrimal eye glands. Clinical signs are typically unilateral and, result in an inability to move the eyelids (inability to blink), inability to move the lips (dogs may accidentally chew on their lips), lack of ear movement (especially noticeable in cats), and a dry, red eye with possible ocular ulceration.

Clinical Course
Signs are typically acute in nature with rapid progression to full clinical manifestation. Spontaneous resolution occurs in 3-6 weeks. Yay!

Management
Supportive care, such as eye lubricant, and ensuring lip injury is minimized by limiting chewing toys/bones, is the mainstay treatment. Antibiotics, steroids, NSAIDs and other medications do not improve the recovery time!

It's short and sweet this week. Please let me know if you have a specific topic of interest! Have a great week, and keep those consults coming.

Consults are available Monday-Saturday at various times. Check out www.barnesveterinaryservices.com (press the schedule button in the upper right corner) to schedule. Note: Only veterinarians or veterinary staff may schedule a consult.