Changes

====Clinical Signs====

====Clinical Signs====

The disease onset may be acute, peracute or chronic.  An insidious onset ataxia is most typical and with such cases, the clinical examination may reveal a bright, alert horse, perhaps with some focal muscle atrophy.(Furr)In all cases, the clinical signs are referable to diffuse focal and multifocal lesions of the white and grey matter of the spinal cord and brain. (EPM3)The three characteristic 'As' (ataxia, asymmetry, atrophy) suggest multifocal or diffuse disease, but are not pathognomonic for EPM (Furr).   

The disease onset may be acute, peracute or chronic.  An insidious onset ataxia is most typical and with such cases, the clinical examination may reveal a bright, alert horse, perhaps with some focal muscle atrophy.<ref name="Furr">Furr, M (2010) ''Equine protozoal myeloencephalitis'' in Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) '''Equine Internal Medicine''' (Third Edition), ''Saunders'', Chapter 12.</ref>  In all cases, the clinical signs are referable to diffuse focal and multifocal lesions of the white and grey matter of the spinal cord and brain. (EPM3)The three characteristic 'As' (ataxia, asymmetry, atrophy) suggest multifocal or diffuse disease, but are not pathognomonic for EPM.<ref name="Furr">Furr, M (2010) ''Equine protozoal myeloencephalitis'' in Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) '''Equine Internal Medicine''' (Third Edition), ''Saunders'', Chapter 12.</ref>  

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*Apparent lameness, particularly atypical or slight gait asymmetry of hindlimbs (not alleviated by local anaesthesia)

*Apparent lameness, particularly atypical or slight gait asymmetry of hindlimbs (not alleviated by local anaesthesia)

*Abnormal placing reactions  

*Abnormal placing reactions  

*Focal muscle atrophy of individual muscle groups(Pasq), especially gluteal muscles, often asymmetrical  

*Focal muscle atrophy of individual muscle groups<ref name="Pasq">Pasquini, C, Pasquini, S, Woods, P (2005) '''Guide to Equine Clinics Volume 1: Equine Medicine''' (Third edition), ''SUDZ Publishing'', 245-250.</ref>, especially gluteal muscles, often asymmetrical  

*Generalized muscle atrophy or loss of condition

*Generalized muscle atrophy or loss of condition

*Localized sensory deficits and 'strip sweating' of dermatomes

*Localized sensory deficits and 'strip sweating' of dermatomes

*Sacrococcygeal involvement will produce signs that mimic ''polyneuritis equi''  

*Sacrococcygeal involvement will produce signs that mimic ''polyneuritis equi''  

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|'''Peripheral nerves''' (may lead to injuries to muscle tendons or ligaments)

|'''Peripheral nerves'''

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*Upward fixation of the patella

*Upward fixation of the patella

*Gait abnormality

*Gait abnormality

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|'''Brainstem''' (cranial nerve signs, <5% cases)

|'''Brainstem''' (cranial nerve signs)

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*Atrophy of ''temporalis'' and ''masseter'' muscles, loss of facial sensation (V)

*Atrophy of ''temporalis'' and ''masseter'' muscles, loss of facial sensation (V)

*Laryngeal hemiplegia (X)

*Laryngeal hemiplegia (X)

*Abnormal menace response (II, VII)

*Abnormal menace response (II, VII)

*Headshaking(EPM 7)

*Headshaking<ref>Moore, L.A, Johnson, P.J, Messer, N.T, Kline, K.L, Crump, L.M, Knibb, J.R (1997) Management of headshaking in three horses by treatment for

*Blindness with or without abnormal pupillary reflexes (Pasq)

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*Blindness with or without abnormal pupillary reflexes,<ref name="Pasq">Pasquini, C, Pasquini, S, Woods, P (2005) '''Guide to Equine Clinics Volume 1: Equine Medicine''' (Third edition), ''SUDZ Publishing'', 245-250.</ref>

|'''Cerebrum, basal nuclei, cerebellum'''

|'''Cerebrum, basal nuclei, cerebellum'''

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*Abnormal menace response

*Abnormal menace response

*Circling

*Circling

*Seizures (may be the only clinical sign)(82 in Furr)

*Seizures (may be the only clinical sign)<ref>Dunigan, C.E, Oglesbee, M.J, Podell, M 'et al.' (1995) Seizure activity associated with equine protozoal myeloencephalitis, ''Prog Vet Neurol'', 6:50-54.  In: Furr, M (2010) ''Equine protozoal myeloencephalitis'' in Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) '''Equine Internal Medicine''' (Third Edition), ''Saunders'', Chapter 12.</ref>

*Abnormal electroencephalogram (EEG)  

*Abnormal electroencephalogram (EEG)  

*Asymmetrical central blindness

*Asymmetrical central blindness

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Lesions of the brainstem, cerebrum or cerebellum are less frequently recognized than those of the spinal cord.  Horse with severe EPM may be unable to stand or swallow and, if left untreated, progress to recumbency within 14 days to 6 months. (Pasq) This deterioration may occur smoothly or spasmodically (Merck) but is likely to result in death.  It has been suggested that rapidly progressive presentations reflect brainstem lesions.(Furr)

Lesions of the brainstem, cerebrum or cerebellum are less frequently recognized than those of the spinal cord.  Horse with severe EPM may be unable to stand or swallow and, if left untreated, progress to recumbency within 14 days to 6 months.<ref name="Pasq">Pasquini, C, Pasquini, S, Woods, P (2005) '''Guide to Equine Clinics Volume 1: Equine Medicine''' (Third edition), ''SUDZ Publishing'', 245-250.</ref> This deterioration may occur smoothly or spasmodically (Merck) but is likely to result in death.  It has been suggested that rapidly progressive presentations reflect brainstem lesions.<ref name="Furr">Furr, M (2010) ''Equine protozoal myeloencephalitis'' in Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) '''Equine Internal Medicine''' (Third Edition), ''Saunders'', Chapter 12.</ref> 

====Diagnosis====

====Diagnosis====