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S. Platt1
1College of Veterinary Medicine- University of Georgia, Small Animal Medicine & Surgery, ATHENS, USA
Simon R. Platt BVM&S MRCVS Dipl. ACVIM (Neurology) Dipl.ECVN
University of Georgia, Athens, GA.
There are several broad categories of disease or abnormality that should be considered when determining whether a paroxysmal event is a manifestation of a seizure disorder or not. These include neuromuscular disorders leading to collapse (e.g., Myasthenia gravis), cardiovascular disease causing syncope, sleep related events such as R.E.M. sleep disorder and narcolepsy/ cataplexy as well a new de ned group of disorders of involuntary movement that are predominantly breed related. Obsessive compulsive disorders will also be mentioned based on their stereotypical presentations and similarities to the focal sensory seizures described in veterinary medicine. These disorders will be discussed
in terms of the classical presenting signs and how they may be considered differently from epileptic disorders. Absolute con rmation of the epileptic nature can only be obtained by observing simultaneously the characteristic EEG changes and physical manifestation of the seizures.
(1) Neuromuscular collapse
Activity associated weakness is the most typical clinical sign of neuromuscular disease. The interpretation of the neurological examination may be challenging in these patients. At the time of examination, they may appear normal or only mildly affected; additionally if weakness is exhibited, it is rarely speci cally indicative of nerve, neuromuscular junction or muscle disease.
In a patient with a neuromuscular disorder, observation and gait analysis may detect ventro exion of neck, short- strided gait with over exion of joints (often more evident in the pelvic limbs), a plantigrade and / or palmigrade stance at rest, and generalised decreased muscle tone.
(2) Involuntary Movement Abnormalities
Dyskinesia - is de ned as impairment of the power
of voluntary movements resulting in fragmented or incomplete movements. Dogs reported with these abnormalities may exhibit abnormal postures such as holding up a limb in an attempt to move or adopting
a kyphotic posture of the spine without being able to initiate movement. The pathophysiologic mechanisms underlying these movements are poorly understood, but may represent a central neurotransmitter or pathway abnormality, or possibly a local muscular abnormality. The impaired movement can appear as and have
been termed muscle ‘cramps’ which are de ned as paroxysmal, prolonged and severe contraction of muscles that may be painful and can be either focal or generalized. Examples of diseases associated with cramps which may be dyskinesias include Scotty Cramp, Episodic Falling of Cavalier King Charles spaniels ‘Epileptoid cramping’ of Border terriers,
and extreme generalized muscular stiffness in Male Labrador retrievers. Muscle cramps have also been described secondary to systemic diseases such as hypoadrenocorticism.
Dyskinesias are movement disorders that occur spontaneously during activity or at rest causing involuntary contractions of groups of muscles in a conscious animal. The descriptions of these conditions indicate that the most common clinical sign is that of dystonia causing increased muscle tone in one or several limbs, possibly leading to collapse. The movements
can be triggered by excitement or exercise. The localization of the purported functional neurotransmitter based abnormalities responsible for these disorders may be central or peripheral nervous system. In general, movement disorders may have origins in the cerebrocortical neurons, basal nuclei or peripheral nervous system.
Idiopathic head tremor/head bob - This head tremor syndrome appears to occur without de nable cause
in some breeds such as the Doberman pinschers (especially dogs less than 1 year of age), Boxers and Bulldogs, however, a variety of breeds can be affected. These dogs have no other clinical abnormalities and
are usually young. Head tremors may be either in an
up down or in a side-to-side plane. Sometimes this is referred to as a head bob. Head tremors are usually more prominent when the dog is less active. Also, dogs seem to be able to stop this movement if they desire, are conscious, can walk and can respond to verbal commands. This is almost the opposite of an intention tremor, as the tremor can be stopped when the dog is focused on a goal-orientated task such as eating. The pathogenesis of this disease is not known. In human
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