Pathognomonic What These Neurologic Signs Mean

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Avis Norris
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1 Pathognomonic What These Neurologic Signs Mean Johnny Randy Cross, DVM, DACVIM (Neurology), Neurosurgery Certificate ACVIM No disease is ever pathognomonic based on clinical signs. However, when given the right history, signalment, and clinical signs, certain diseases become the overwhelming likelihood. There are variations in each of these diseases but this lecture will focus on the classic examples. There are esoteric diseases out there, but in this lecture we try to look at diseases that you will see in private practice. The discussion will be on their signalment, history, clinical signs, treatment and prognosis. Certainly diagnostics are going to be necessary to confirm the suspicion and rule out other possible causes, but are not covered here. 1. Feline Aortic Thromboembolism (FATE) i. Typically older cats ii. Heart disease, hyperthyroidism, hypertension, or renal disease 1. Many papers have demonstrated that the owners are unaware of the heart disease. Heart disease is often discovered at the time presentation for the FATE. iii. Acute onset i. Heart murmur with tachypnea ii. Paraparesis or paraplegia iii. Firm pelvic limb muscles that are swollen and painful iv. Unable to flex the tarsal joint v. No palpable femoral pulses vi. Cold limbs vii. Pale to blue nail beds i. No proven treatment ii. Identifying the underlying cause is the best way to treat iii. No proven difference between aspirin and clopidogrel 1. Clopidogrel probably safer but true safety study has not been performed. iv. Chance of being discharged is 50%. 1. However, those that are discharged have a 50-75% chance of relapse v. Negative prognostic indicators 1. Less than 99 degree rectal temperature 2. Bilateral limb involvement 3. Paraplegia 4. Hyperphosphatemia 5. Bradycardia 2. Trigeminal Nerve Sheath Tumor

2 i. Older dogs and rarely cats 1. Really rare in a patient less than 3 years old ii. Persistent and slow worsening atrophy of the muscles of mastication 1. This is a tricky area because more often than not, an owner will claim that they noticed the muscle loss overnight. So don t let an owner s impression of the onset of signs throw you. Acute awareness of disease is not tantamount to acute onset of disease. iii. Sometimes the owner will not notice the temporalis muscle atrophy but complain of a sunken eye. iv. An owner might comment on how a bone (zygomatic arch) is protruding from the dogs face. Obviously not a protrusion, just loss of the surrounding muscles. v. A dropped jaw is not part of this history. It takes disease of both trigeminal nerves to drop the jaw. i. Ipsilateral atrophy of the muscles of mastication (notably the temporalis) ii. Ipsilateral hypalgesia of the face. The trigeminal nerve provides sensation to the face and therefore the sensory branches can become affected. iii. Occasionally there will be Horner Syndrome (enophthalamos, miosis, ptosis, third eyelid protrusion) i. Surgery is the best way to treat these. Unfortunately, it is hard to get the tumor proximal enough to remove it all. ii. Unclear if radiation is helpful. iii. Steroids are helpful when intracranial signs are seen from the tumor growing proximally toward the pons. iv. Fortunately, even patients that do not have surgery or radiation can live a long time. Some dogs will survive up to 2 years without treatment. 3. Idiopathic Trigeminal Neuritis i. Primarily dogs, rarely in cats ii. Middle-aged most often (usually about 5 years old) iii. Golden Retrievers overrepresented iv. Owners usually complain about a: 1. Dropped jaw 2. Difficulty eating 3. Drooling. An owner may describe this as hypersalivation when in reality they are just not swallowing well i. Acute onset of an inability of the patient to spontaneously close their jaw ii. The jaw can be manually closed very easily.

3 iii. About 1/3 of cases will also have altered sensation to the face. iv. Nota Bene = People often confuse this disease with masticatory muscle myositis (MMM). In MMM, the patient might hold the jaw open slightly since it is painful to move it, but able to close their jaw. These patients are painful upon palpation of their masticatory muscles and very painful upon opening of their jaw. i. Excellent prognosis ii. Recovery time on average is 22 days. iii. Do not treat with steroids. If a patient has a different disease then you might be masking their clinical signs. Additionally, it does not speed the recovery of idiopathic trigeminal neuritis iv. It must be said that a dropped jaw can be a manifestation of rabies. Therefore, be cautious in your history taking with respect to vaccine history, possible exposure and other clinical signs. 4. Idiopathic Head Bobbing i. Usually 6 months to 2 years old ii. Bulldog is classic breed. Also common in boxers, Labrador retrievers and Doberman pinschers. iii. Intermittent vertical or horizontal head bobbing that ceases with activity 1. This is opposite of an intention tremor. Intention tremors occur or get worse when a patient is focused on something. With idiopathic head bobbing, the patient will stop if they start walking, eating, or are distracted with a toy. 2. The interruptible nature makes a partial seizure less likely. i. Neurological and physical exams are normal. ii. There is no neck pain. i. No treatment is necessary. ii. Prognosis is excellent iii. Often the episodes will cease after a couple of months but recurrence is possible 5. Metronidazole Toxicity i. Any age dog and, less commonly but possible, cat. ii. Average metronidazole dose is 60 mg/kg/day and average duration 40 days 1. However, any dose or duration is possible iii. Acute onset of vestibular or cerebellar signs i. Most commonly vestibular and cerebellar signs (nystagmus, head tilt, falling to both sides while walking,

4 ii. Severe cases can become comatose, have convulsions, and be opisthotonic iii. Cats can present with blindness as well iv. Interestingly, when picked up off the ground these dogs will often lift their thoracic limbs up and place them on the side of their heads. This is likely a compensation for their feeling off balance but I think they are telling you where the problem is occurring. i. Treat with diazepam 0.5mg/kg PO TID for 3 days 1. Dogs treated with diazepam recover on average in 2 days 2. Dogs without diazepam recover on average in 12 days ii. Prognosis is excellent with chance of some residual signs possible. iii. Take away Any patient that has vestibular or cerebellar signs and has an acute onset of disease should be asked if they are on metronidazole 6. Focal Tetanus Barn Cat i. Typically young cats ii. Any cat with a recent history of being neutered in an unsanitary environement 1. This can occur in a veterinary clinic but more often it will be the veterinarian that performs the procedure out at the barn. iii. Acute onset of clinical signs usually 1-2 weeks after the neuter i. Rigid extension of one of the pelvic limbs 1. Focal tetanus is the hallmark of this disease but remember that tetanus can be focal or generalized. 2. This limb is often held backwards 3. Watching a video of this is probably the most helpful way to remember what this looks like i. Nota Bene = Tetanus is the likely result of an ongoing infection where the toxin is being absorbed from the site of infection. This is unlike botulism in small animals where the toxin is ingested but active infection within the patient is less likely. ii. Search for the wound so that it may be cleaned. If the wound is open, like a neuter might be, flushing with chlorhexidine or hydrogen peroxide is best. iii. Antibiotics are absolutely necessary. Penicillin G or metronidazole is best. 1. A wound can also be infused with penicillin G 2. Duration should be 2 weeks iv. Muscle relaxants are often ineffective but still should be administered. Diazepam and methocarbamol are preferred. v. Although anti-toxin is a consideration, it is not widely available to veterinarians. vi. Keep the patient calm as stimulation will exacerbate the muscle contraction.

5 vii. Pain medications can help to slightly sedate some patients and treat pain associated with the muscle contraction. viii. Prognosis is good. 7. Dancing Doberman i. Only seen in the Doberman Pinscher ii. Usually a couple years old but can be from 6 months to 7 years old. iii. Usually starts with holding one of the pelvic limbs up intermittently. Progresses to alternating from one pelvic limb to the other iv. Owners will describe this as shifting back and forth v. This is an excellent case for the owner to obtain a video so you can see exactly what the patient is doing. i. Normal neurological and orthopedic exam. ii. No lameness or ataxia is noted on examination. iii. These patients often sit when given the chance as opposed to standing. iv. Occasionally in advanced forms of the disease the patient will have some postural reaction deficits. v. No signs of polyarthropathy are seen as this could present in a similar fashion. Polyarthropathy would have swollen, hot and painful joints. i. There is no effective treatment. ii. Prognosis remains good for quality of life but clinical signs often persist. References: Lorenz MD, Coates JR, Kent M (2011) Handbook of Veterinary Neurology. St. Louis, Missouri: Elsevier Dewey CW (2008) A practical guide to canine and feline neurology. Ames, Iowa. Wiley-Blackwell

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