Motor neuron disease: inherited and acquired

Diagnosis and Treatment of Lower Motor Neuron Disease in Australian Dogs and Cats

Diseases presenting with lower motor neuron (LMN) signs are frequently seen in small animal veterinary practice in Australia. In addition to the most common causes of LMN disease seen world-wide, such as idiopathic polyradiculoneuritis and myasthenia gravis, there are several conditions presenting with LMN signs that are peculiar to the continent of Australia. These include snake envenomation by tiger (Notechis spp.), brown (Pseudonaja spp.), and black snakes (Pseudechis spp.), tick paralysis associated with Ixodes holocyclus and Ixodes coronatus, and tetrodotoxins from marine animals such as puffer fish (Tetraodontidae spp.) and blue-ring octopus (Hapalochlaena spp.). The wide range of differential diagnoses along with the number of etiological-specific treatments (e.g., antivenin, acetylcholinesterase inhibitors) and highly variable prognoses underscores the importance of a complete physical exam and comprehensive history to aid in rapid and accurate diagnosis of LMN disease in Australian dogs and cats. The purpose of this review is to discuss diagnosis and treatment of LMN diseases seen in dogs and cats in Australia.

Classification of involuntary movements in dogs: Tremors and twitches

This review focuses on important new findings in the field of involuntary movements (IM) in dogs and illustrates the importance of developing a clear classification tool for diagnosing tremor and twitches. Developments over the last decade have changed our understanding of IM and highlight several caveats in the current tremor classification. Given the ambiguous association between tremor phenomenology and tremor aetiology, a more cautious definition of tremors based on clinical assessment is required. An algorithm for the characterisation of tremors is presented herein. The classification of tremors is based on the distinction between tremors that occur at rest and tremors that are action-related; tremors associated with action are divided into postural or kinetic. Controversial issues are outlined and thus reflect the open questions that are yet to be answered from an evidence base of peer-reviewed published literature. Peripheral nerve hyper-excitability (PNH; cramps and twitches) may manifest as fasciculations, myokymia, neuromyotonia, cramps, tetany and tetanus. It is anticipated that as we learn more about the aetiology and pathogenesis of IMs, future revisions to the classification will be needed. It is therefore the intent of this work to stimulate discussions and thus contribute to the development of IM research.

Fibrinoid leukodystrophy (Alexander's disease-like disorder) in a young adult French bulldog

The paper describes clinical and pathological features of Alexander's disease (AD)-like disorder in a 1 year and 8 months old French bulldog. Clinically, the dog exhibited megaesophagus, emaciation and weakness without any specific neurological symptoms. The dog died of aspiration pneumonia. On the gross observation of formalin-fixed brain, discolored foci were observed in the white matter of the cerebellum and brain stem. Histologically, numerous Rothenthal fibers and hypertrophic astrocytes were distributed especially in the perivascular, subependymal and subpial area of both the cerebrum and cerebellum. The Rosenthal fibers were intensely immunopositive for GFAP and ubiquitin. Demyelination of the white matter was occasionally found in the brain stem. The present case is likely to be categorized in the adult form of AD, though previous AD-like cases in dogs were in the juvenile form.

Acquired motor neuron loss causing severe pelvic limb contractures in a young cat

PRESENTATION

This report describes a kitten with paraplegia and extensor rigidity of the pelvic limbs associated with motor neuron loss and chronic denervation of skeletal muscle. Persistent skeletal muscle atrophy and degeneration had resulted in immobile stifle and hock joints and severe pelvic limb rigidity consistent with a neurogenic form of arthrogryposis. Both pelvic limbs were equally affected and the kitten showed no signs of pain.

INVESTIGATIONS

Electromyography identified spontaneous activity in the pelvic limbs. Muscle and peripheral nerve biopsies showed pathology consistent with denervation. On necropsy, 3 weeks after admittance, severe degenerative changes including axonal necrosis and myelin degeneration were confirmed in the lumbar spinal cord.

CLINICAL RELEVANCE

There are very few descriptions of feline motor neuron degeneration in the literature and obtaining an ante-mortem diagnosis is difficult. Although an inherited disorder cannot be ruled out, a condition acquired congenitally in utero or postnatally was suspected in this case.

Pediatric Neurology of the Dog and Cat

The neurologic examination in the puppy or kitten can be a challenging experience. Understanding the development of behavior reflexes and movement in puppies and kittens enables us to overcome some of these challenges and to recognize the neurologically abnormal patient. Subsequently,we can identify the neuroanatomic localization and generate a differential diagnosis list. This article first reviews the pediatric neurologic examination and then discusses diseases unique to these individuals.