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Equine Protozoal Myeloencephalitis (view source)
Revision as of 18:37, 19 July 2010
, 18:37, 19 July 2010→Clinical Signs
====Clinical Signs====
====Clinical Signs====
S neurona produces signs relating to diffuse, focal and multifocal lesions of the white and grey matter of the spinal cord and brain (EPM 3).
Ataxia or paresis of one or more limbs: stumbling, falling, knuckling and toe dragging.
Sacrococcygeal involvement: mimics polyneuritis equi.
Cranial nerve signs: loss of tongue tone, loss of sensation to the face and unilateral facial paralysis. Brain involvement: dysphagia, circling, head tilt or recumbency(EPM3)
Signs: asymmetrical weakness, ataxia, vestibular disease (peripheral or central) peripheral neuropathy, ill-defined hindlimb lameness, asymmetric muscle atrophy. (Vetstream)
Variable onset of disease:
*Chronic - insidious in onset and difficult to diagnose.
*Acute.
*Peracute.
Spinal cord infection :
*Ataxia and weakness (hindlimbs > forelimbs) - often asymmetrical.
*Apparent lameness, particularly atypical or slight gait asymmetry of hindlimbs (not alleviated by local anesthesia).
*Abnormal placing reactions.
*Focal muscle atrophy (individual muscle grps (Pasq)- evident anywhere especially gluteal muscles - often asymmetrical.
*Generalized muscle atrophy/loss of condition
Lesions of the brainstem, cerebrum or cerebellum are less frequently recognized:
Cranial nerve dysfunction (<5% of cases) - any can be affected:
*Atrophy of temporalis/masseter muscles (V)
*Dysphagia (V, VII, IX, X, XII)
*Abnormalities of facial (VII) and vestibulocochlear (VIII) nerves often observed together:
*VIII - vestibular signs of nystagmus, head tilt, base-wide stance
*VII - muzzle deviation, ptosis, ear droop
*Dorsal displacement of soft palate (IX, X)
*Laryngeal hemiplegia (X)
Severe cases may:
*Inability to stand.
*Inability to swallow.
Infection of cerebrum, basal nuclei, cerebellum:
Focal cerebral problems:
*Seizures.
*Abnormal EEG.
*Asymmetrical central blindness
*Facial hypalgesia
*Cerebellar ataxia
*Altered behavior
*Depression
*Narcolepsy-like syndrome
Nerve damage/ataxia injuries to muscle tendons or ligaments:
*Upward fixation of the patella
*Exertional rhabdomyolysis .
*Back pain.
*Gait abnormality.
Any gait abnormality in galloping/trotting race/dressage horses while in training which cannot be attributed to musculoskeletal abnormality may result from EPM and requires careful neurologic evaluation.(Vetstream)
Headshaking(EPM 7)
Gait abnormality (peracute or acute) - 1 or all 4 limbs depending on where migrates, asymmetrical (because multifocal), ataxia, paresis & spasticity - knuckling, circumduction, crossing over, tetraparesis - areflexia, hyporeflexia (LMN) or hyperreflexia (UMN) depending on site of lesion, localized areas of sensory deficits, 'strip sweating' localized areas (dermatomes, sympathetic white matter tracts), cerebellar, brain stem (less common) or cerebral signs, cranial nn - head tilt, facial paralysis, circling, nystagmus, dysphagia, blindness with or without abnormal pupillary reflexes, untreated progressive to recumbency in 14days to 6mths (Pasq)
The three characteristic 'As' of EPM (ataxia, asymmetry, atrophy) suggest multifocal or diffuse disease, but are not pathognomonic. It has been suggested that rapidly progressive presentations reflect brainstem lesions. Spinal cord signs are most commonly seen and may include:
*asymmetric or symmetric paresis, spasticity and ataxia of one to four limbs
*focal or general muscle atrophy
*apparent lameness
*back pain
*loss of reflexes or cutaneous anaesthesia
*abnormal menace response
Without treatment, progression to recumbency and death is likely. This deterioration may occur smoothly or spasmodically over hours to years. (Merck)
====Diagnosis====
====Diagnosis====