Neurology SBAs Flashcards
Scenario: During a neurological examination of a horse, you observe a menace response in the left eye but not the right. All other cranial nerve functions appear normal.
Lead-in: Which cranial nerve is primarily being assessed by the menace response?
Options:
a) Optic nerve (CN II)
b) Oculomotor nerve (CN III)
c) Trochlear nerve (CN IV)
d) Trigeminal nerve (CN V)
e) Abducens nerve (CN VI)
Answer: a) Optic nerve (CN II)
Explanation: The menace response assesses the optic nerve (afferent pathway) and the facial nerve (efferent pathway). A lack of response suggests a lesion in either of these nerves or the pathways connecting them.
Scenario: A horse with a suspected neurological condition exhibits a head tilt and leans towards the left.
Lead-in: These clinical signs are most suggestive of dysfunction in which part of the nervous system?
Options:
a) Forebrain
b) Cerebellum
c) Vestibular system
d) Spinal cord
e) Peripheral nerves
Answer: c) Vestibular system
Explanation: Head tilt and leaning are classic signs of vestibular dysfunction, which is responsible for balance and spatial orientation.
Scenario: A horse with normal mentation shows ataxia characterised by crossing of the hind limbs and knuckling of the fetlocks.
Lead-in: This type of ataxia is most consistent with which type of neurological deficit?
Options:
a) Vestibular
b) Cerebellar
c) Spinal (proprioceptive)
d) Forebrain
e) Cranial nerve
Answer: c) Spinal (proprioceptive)
Explanation: Crossing of the limbs and knuckling are indicative of proprioceptive deficits, which result from dysfunction of the ascending pathways in the spinal cord.
Scenario: A young horse (2 years old) presents with progressive ataxia and weakness, particularly affecting the hind limbs. The horse has normal mentation.
Lead-in: Which of the following conditions is a common cause of this presentation in this age group?
Options:
a) Equine Protozoal Myeloencephalopathy (EPM)
b) Cervical Vertebral Compressive Myelopathy (CVCM)
c) Equine Herpesvirus Myeloencephalopathy (EHM)
d) Rabies
e) Tetanus
Answer: b) Cervical Vertebral Compressive Myelopathy (CVCM)
Explanation: Cervical Vertebral Compressive Myelopathy (CVCM), also known as Wobbler syndrome, is a common cause of progressive ataxia and weakness, especially in the hind limbs, in young horses.
Scenario: A horse develops acute onset ataxia, weakness, and urinary incontinence. The horse had a fever 5 days prior that resolved spontaneously.
Lead-in: Which of the following is the most likely aetiology?
Options:
a) Head trauma
b) Hepatic encephalopathy
c) Equine Herpesvirus Myeloencephalopathy (EHM)
d) Rabies
e) Botulism
Answer: c) Equine Herpesvirus Myeloencephalopathy (EHM)
Explanation: The acute onset of neurological signs, particularly ataxia, weakness, and urinary incontinence, often following a fever, is highly suggestive of Equine Herpesvirus Myeloencephalopathy (EHM) due to EHV-1.
Scenario: A horse with normal mentation exhibits a wide-based stance and dysmetria (hypermetria).
Lead-in: These signs are most indicative of dysfunction in which part of the nervous system?
Options:
a) Spinal cord
b) Vestibular system
c) Cerebellum
d) Forebrain
e) Peripheral nerves
Answer: c) Cerebellum
Explanation: A wide-based stance and dysmetria (abnormal limb movements, often exaggerated) are characteristic signs of cerebellar ataxia.
Scenario: A horse shows involuntary, sudden, violent, repetitive movements of the head.
Lead-in: This clinical sign is characteristic of which condition?
Options:
a) Narcolepsy
b) Head-shaking
c) Shivers
d) Seizures
e) Vertigo
Answer: b) Head-shaking
Explanation: Head-shaking is defined by involuntary, sudden, violent, and repetitive movements of the head, which can be dorso-ventral, horizontal, or rotational.
Scenario: A horse suddenly collapses and appears to fall asleep during the day, but is easily rousable.
Lead-in: This clinical presentation is most consistent with which neurological condition?
Options:
a) Sleep deprivation
b) Narcolepsy
c) Seizures
d) Syncope
e) Catalepsy
Answer: b) Narcolepsy
Explanation: Narcolepsy in horses is characterised by sudden episodes of sleep during the day, often associated with cataplexy (sudden muscle weakness), and the horse is usually easily rousable.
Scenario: A horse exhibits a gait characterised by involuntary trembling of the hind limbs, particularly when asked to back up.
Lead-in: This gait abnormality is most suggestive of which condition?
Options:
a) Stringhalt
b) Shivers
c) Ataxia
d) Hypermetria
e) Hypometria
Answer: b) Shivers
Explanation: Shivers is a neuromuscular condition in horses characterised by involuntary trembling of the hind limbs, often most apparent when backing or lifting a hind limb.
Scenario: A horse with reduced mentation is exhibiting compulsive circling to the right and appears blind, but has normal pupillary light reflexes.
Lead-in: These signs are most suggestive of a lesion in which part of the brain?
Options:
a) Brainstem
b) Cerebellum
c) Left forebrain
d) Right forebrain
e) Spinal cord
Answer: d) Right forebrain
Explanation: Circling is often towards the side of a forebrain lesion. Blindness with normal pupillary light reflexes suggests a central (forebrain) lesion affecting vision pathways. Reduced mentation also points to forebrain involvement.
Scenario: A horse with a history of liver disease develops neurological signs including head pressing and aimless wandering.
Lead-in: What is the most likely underlying cause of these neurological signs?
Options:
a) Head trauma
b) Rabies
c) Hepatic encephalopathy
d) West Nile Virus
e) Tetanus
Answer: c) Hepatic encephalopathy
Explanation: Hepatic encephalopathy occurs due to the accumulation of toxins in the bloodstream that are normally cleared by the liver, leading to neurological signs such as altered mentation, head pressing, and ataxia.
Scenario: A horse that recently sustained a head injury is obtunded and has anisocoria (unequal pupil size).
Lead-in: Anisocoria in this context most likely indicates which of the following?
Options:
a) Cerebellar dysfunction
b) Increased intracranial pressure
c) Vestibular disease
d) Spinal cord trauma
e) Peripheral nerve damage
Answer: b) Increased intracranial pressure
Explanation: Anisocoria following head trauma can be a sign of increased intracranial pressure, potentially due to brain swelling or haemorrhage, affecting the oculomotor nerve.
Scenario: A horse presents with muscle stiffness, a sawhorse stance, and prolapse of the third eyelid. The owner reports a recent wound.
Lead-in: These clinical signs are highly suggestive of which condition?
Options:
a) Botulism
b) Rabies
c) Tetanus
d) West Nile Virus
e) Equine Encephalomyelitis
Answer: c) Tetanus
Explanation: The clinical signs of muscle stiffness, sawhorse stance, prolapse of the third eyelid, and a history of a wound are classic for tetanus, caused by the neurotoxin tetanospasmin.
Scenario: A horse develops progressive paralysis, starting with the tail and progressing to involve the limbs. The horse is bright and alert.
Lead-in: This clinical presentation is most consistent with which condition?
Options:
a) Tetanus
b) Rabies
c) Botulism
d) Equine Herpesvirus Myeloencephalopathy (EHM)
e) West Nile Virus
Answer: c) Botulism
Explanation: Botulism, caused by the neurotoxin botulinum, leads to progressive, flaccid paralysis, often starting with the tail and progressing cranially. Mentation usually remains normal.
Scenario: A horse that was grazing in a field develops ataxia, muscle tremors, and a stilted gait. The pasture contains perennial ryegrass.
Lead-in: Which of the following is the most likely cause of these neurological signs?
Options:
a) Tetanus
b) Botulism
c) Ryegrass staggers
d) Equine Protozoal Myeloencephalopathy (EPM)
e) West Nile Virus
Answer: c) Ryegrass staggers
Explanation: Ryegrass staggers is a neurological condition in horses caused by toxins produced by endophytes in perennial ryegrass, leading to ataxia, tremors, and a stilted gait.
Scenario: A horse with suspected neurological disease has a cerebrospinal fluid (CSF) tap performed.
Lead-in: What is the most common site for CSF collection in the standing sedated horse?
Options:
a) Atlanto-occipital space
b) Lumbo-sacral space
c) Cervical vertebrae (C6-C7)
d) Thoracic vertebrae (T10-T11)
e) Coccygeal vertebrae
Answer: a) Atlanto-occipital space
Explanation: The atlanto-occipital space, located between the occipital bone and the atlas (first cervical vertebra), is the most common and safest site for CSF collection in the standing sedated horse.
Scenario: A horse with ataxia has a CSF tap performed. The CSF analysis reveals increased protein and a mononuclear pleocytosis.
Lead-in: These findings are most consistent with which type of neurological condition?
Options:
a) Toxin-induced neuropathy
b) Viral encephalitis/myelitis or protozoal myelitis
c) Cerebellar degeneration
d) Traumatic brain injury
e) Metabolic encephalopathy
Answer: b) Viral encephalitis/myelitis or protozoal myelitis
Explanation: Increased protein and a mononuclear pleocytosis in the CSF are typical findings in inflammatory neurological conditions such as viral encephalitis/myelitis (e.g., EEE, WEE, WNV) or protozoal myelitis (EPM).
Scenario: A horse with suspected Cervical Vertebral Compressive Myelopathy (CVCM) undergoes cervical radiography.
Lead-in: What is a key radiographic finding suggestive of CVCM?
Options:
a) Fractured cervical vertebra
b) Osteoarthritis of the cervical facet joints
c) Narrowing of the vertebral canal
d) Presence of a vertebral abscess
e) Luxation of the atlanto-occipital joint
Answer: c) Narrowing of the vertebral canal
Explanation: Cervical radiography in horses with CVCM may reveal a narrowing of the vertebral canal, particularly at specific vertebral junctions, leading to compression of the spinal cord.
Scenario: A horse with head trauma is comatose and has fixed, dilated pupils.
Lead-in: These signs indicate a poor prognosis and suggest severe damage to which part of the brain?
Options:
a) Cerebellum
b) Forebrain
c) Brainstem
d) Spinal cord
e) Peripheral nerves
Answer: c) Brainstem
Explanation: Fixed and dilated pupils in a comatose horse with head trauma suggest severe brainstem damage, which carries a grave prognosis due to the brainstem’s role in vital functions.
Scenario: A horse with suspected Equine Protozoal Myeloencephalopathy (EPM) is being evaluated.
Lead-in: Which of the following is a common diagnostic test for EPM?
Options:
a) Complete blood count
b) Serum biochemistry panel
c) Antibody testing in serum and cerebrospinal fluid
d) Electroencephalogram (EEG)
e) Muscle biopsy
Answer: c) Antibody testing in serum and cerebrospinal fluid
Explanation: Diagnosis of EPM often involves testing for antibodies against Sarcocystis neurona in both serum and cerebrospinal fluid to assess for exposure and potential central nervous system involvement.
Scenario: A horse with head-shaking is being investigated.
Lead-in: Which nerve is responsible?
Options:
a) Olfactory nerve (CN I)
b) Optic nerve (CN II)
c) Trigeminal nerve (CN V)
d) Facial nerve (CN VII)
e) Vagus nerve (CN X)
Answer: c) Trigeminal nerve (CN V)
Explanation: Trigeminal-mediated head-shaking is thought to involve abnormal sensory function of the trigeminal nerve, leading to facial pain or paraesthesia.
Scenario: A horse with suspected botulism is presented.
Lead-in: What is a characteristic clinical sign of botulism in horses?
Options:
a) Muscle rigidity
b) Hypermetria
c) Progressive, flaccid paralysis
d) Seizures
e) Head tilt
Answer: c) Progressive, flaccid paralysis
Explanation: Botulism causes a progressive, flaccid paralysis due to the botulinum toxin blocking the release of acetylcholine at neuromuscular junctions.
Scenario: A horse with a neurological condition is being assessed for prognosis.
Lead-in: Which of the following is generally considered a poor prognostic indicator in horses with neurological disease?
Options:
a) Normal mentation
b) Presence of cranial nerve deficits
c) Ambulatory status
d) Improvement with treatment
e) Acute onset of signs
Answer: b) Presence of cranial nerve deficits
Explanation: Cranial nerve deficits often indicate involvement of the brainstem, which controls vital functions, and their presence is generally associated with a poorer prognosis in horses with neurological disease.
Scenario: A horse with suspected Vitamin E deficiency myeloencephalopathy is being evaluated.
Lead-in: Which of the following breeds has a recognised predisposition for this condition?
Options:
a) Thoroughbred
b) Standardbred
c) Arabian
d) Warmblood
e) Friesian
Answer: d) Warmblood
Explanation: Warmblood horses, particularly during pregnancy, have been recognised to be predisposed to Vitamin E deficiency myeloencephalopathy.
