Top 15 Equine Neurological Disorders: A Comprehensive NAVLE Guide (Part 1)
Introduction
Equine neurological disorders present a complex challenge for veterinary professionals. This guide provides essential information on the most critical conditions, offering insights into diagnosis and treatment to help prepare for the NAVLE.
1. Equine Protozoal Myeloencephalitis (EPM)
Classic Case:
EPM is more common in younger horses under four years old, presenting a wide range of neurological signs due to multifocal lesions in the spinal cord and brainstem. Asymmetric ataxia and muscle atrophy are typical symptoms.
Diagnosis:
- Etiology: Mainly caused by Sarcocystis neurona, occasionally Neospora hughesi.
- Diagnostic Approach: Combination of clinical history, geography, and elimination of other diseases.
- Gold Standard: Serumtiter ratio, SAG2,4/3 titer (ELISA) for S. neurona.
Treatment:
- Antiprotozoal Therapy: Ponazuril or diclazuril are safe options.
- Supportive Care: Includes short-term anti-inflammatory drugs and stress minimization.
Pearls:
The prognosis is guarded to fair, with less severe symptoms often resulting in better outcomes. Preventative measures include keeping opossums away and minimizing stress.
2. Cervical Vertebral Malformation & Malarticulation (CVM)
Classic Case:
Known as “wobblers,” CVM is common in young horses, particularly Thoroughbreds and Warmbloods, and presents as progressive ataxia and weakness. It can be developmental (Type I) or acquired (Type II).
Diagnosis:
- Etiology: Developmental or due to osteoarthritis/trauma.
- Imaging: Spinal radiography and myelography reveal vertebral canal stenosis and angular deformities.
Treatment:
- Surgical: Decompression and fusion.
- Management: Calorie and exercise restriction for young horses, NSAIDs, and possible vertebral facet injections for older horses.
Pearls:
The prognosis varies, with single-site involvement having a better outlook than multiple sites.
3. Central Nervous System Injury
Classic Case:
Occurs in young, athletic horses with a history of trauma. Symptoms depend on the injury site and can include ataxia, strabismus, and facial nerve deficits.
Diagnosis:
- Imaging: Skull and spinal radiographs, MRI/CT.
- Assessment: CSF analysis if the injury is uncertain.
Treatment:
- Immediate Care: Manage airway, stop bleeding, and treat shock.
- Medications: Diazepam for seizures, NSAIDs for pain, and mannitol for coma.
Pearls:
Prognosis is guarded, depending on the injury’s location and severity, with brain injuries having a higher survival rate.
4. Clostridial Neurotoxins: Botulism and Tetanus
Classic Case:
- Botulism: Presents as flaccid tetraparesis and dysphagia. Common in foals (“shaker foal syndrome”).
- Tetanus: Stiff gait, dysphagia, and hypersensitivity. Often follows recent injury or surgery.
Diagnosis:
- Botulism: PCR or mouse bioassay, grain test, and EMG.
- Tetanus: Based on history and clinical signs.
Treatment:
- Botulism: Antibiotics, antiserum, and supportive care.
- Tetanus: Sedation, wound cleaning, antibiotics, and tetanus antitoxin.
Pearls:
Prognosis for botulism varies, with recumbent adults having a poor outcome. Tetanus prognosis improves if the animal is not recumbent.
5. Equine Degenerative Myelopathy (EDM)/Equine Motor Neuron Disease (EMND)
Classic Case:
- EDM: Affects young horses with insidious onset and progressive ataxia.
- EMND: Adult onset with muscle atrophy, weakness, and increased recumbency.
Diagnosis:
- Etiology: Likely due to vitamin E deficiency.
- Tests: Muscle biopsies and EMG for EMND.
Treatment:
- Vitamin E Supplementation: Crucial for managing symptoms and preventing progression.
Pearls:
Both conditions have a guarded prognosis, with treatment helping but not curative. EDM has a familial component, while EMND affects older horses.