ABSTRACT OF THE WEEK

Journal of the American Veterinary Medical Association
Volume 261 | Issue 6 (June 2023)

Difficulty walking and trembling in a 10-year-old female Akita Inu.

J Am Vet Med Assoc. June 2023;261(6):926 - 928.

Evelina Burbaitė, Marika Menchetti

Companion Notes

Case report of orthostatic tremors in a dog

Introduction on primary orthostatic tremors (OTs)

- benign involuntary movement disorder

- usually reported in young giant- or large-breed dogs

- between 9 months and 2 years of age

- but in retrievers it seems to appear later in life

- involves progressive involuntary, high-frequency tremor in hindlimbs

- primarily affecting them during the standing position

- can progress to most often involve the forelimbs

- but also the trunk and head

- affected dogs appear reluctant to lie down

- they can have difficulty in sitting and standing

- tremors can be confused with weakness or exercise intolerance

- typically tremors disappear when affected legs are raised from the ground

- or during walking, sitting, or lying down

- OTs can be divided into primary OT (considered idiopathic) and OT-plus

- OT-plus involves OT in dogs with other concomitant neurological disease

- diagnosis of primary OTs is based on the following:

- typical clinical presentation

- positive weight-bearing lifting test

- conscious EMG in weight-bearing posture showing high-frequency tremors

- “helicopter sign”

- sound resembling a distant helicopter during auscultation with stethoscope

(over limb with tremors)

- in human medicine

- regardless of medication, response is often scarce and minimal

- clonazepam is the 1^st choice

- second-line options include the following:

- gabapentin

- primidone

- sodium valproate

- carbamazepine

- phenobarbital

- deep brain stimulation used successfully

- in canine medicine

- medication options appear to give a higher rate of improvement than humans

- gabapentin and phenobarbital used in most recently published reports

- improvement is usually partial

Case report of 10-year-old 29.3 kg [64.6 lb] neutered sex:F dog

- history of a commercial diet and regular vaccination

- at referral for difficulty in walking and trembling in hindlimbs of 6 years' duration

- tremors progressed in last 4 months, mildly involving the forelimbs

- physical examination: unremarkable

- neurological examination

- limb tremors, while standing

- mostly hindlimbs and very mild in forelimbs

- disappeared in lie-down position

- difficulty in sitting

- positive weight-bearing lifting test

- tremors discontinued after lifting and keeping hindlimbs air-floating

- neurolocalization

- tremors predominantly in limbs

- triggered by standing and discontinuing after keeping hindlimbs air-floating

- and during lie-down position

- suggestive of orthostatic tremors

- lesion involving 1 or more of the following suspected:

(considering recent literature)

- suspect spinal cord lesion involving 1 or more of the following:

- ventral gray column

- α-motor neurons

- spinal cord gray matter interneurons

- intracranial structures (brainstem and cerebellum)

- likely location of lesion using human medicine concerning orthostatic tremors

- central generator, called the “central oscillator,” demonstrated

- located predominantly in cerebellum and brainstem

- but other areas seem to be involved in this circuit

- creating a ponto-cerebello-thalamo-motor cortical activation

- differential diagnoses for a 10-year-old dog with chronic standing tremors

(and difficulty lying down)

- OTs

- benign idiopathic rapid postural tremors

- these appear in older dogs

- not associated with any type of difficulty in lying down

- usually do not disappear with a weight-bearing lifting test

- tremors due to paresis as a consequence of a neuromuscular disease

- causing exercise intolerance and weakness

- neuromuscular disease unlikely

- since evaluation of spinal reflexes was unremarkable

- degenerative lumbosacral stenosis causing cauda equina compression

- degenerative lumbosacral stenosis ruled out due to the following:

- unremarkable lumbosacral area palpation

- unremarkable perineal reflex

- unremarkable extension of the lumbosacral joint

(also called “lordosis test”)

- sciatic nerve malfunction

- chronic orthopedic problems such as hip dysplasia

- CBC and serum biochemistry results considered not clinically relevant

- leukopenia, slight at 4.39 thousands/μL with reference at 5.49-8.23

- high ferritin, mild at 302 ng/mL with reference at 84-247

- hypercholesterolemia at 339 mg/dL with reference at 151-249

- orthopedic examination: unremarkable

- conscious surface electromyography (EMG) of affected limb muscles

- OTs are characterized by pathognomonic high-frequency tremors

- during a standing position

- high-frequency rhythmic spontaneous discharges of 20 Hz recorded

- in all tested limbs

- definitive diagnosis: primary OTs

- treatment

- trial with gabapentin, 3 mg/kg PO bid started

- slowly increased to 5 mg/kg bid

- owner reported no improvement after 3 months of therapy

- dog started showing drowsiness

- owner declined other medical options and gabapentin was stopped

- outcome after 1 year followup, clinical signs unchanged

“The overall prognosis in dogs with OTs is considered to be good, as the disease is benign and slowly progressive.”

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