Chapter 51 - Diagnostic neuro disease Flashcards
What basic equipment is required for a neurologic examination in horses?
A transilluminator, a hemostat, and a pleximeter or patella hammer (for neonates).
hat are the four states of consciousness, and how is each characterized?
Normal (alert and responsive), obtunded (reduced alertness but responsive), stuporous (minimal responsiveness, needs painful stimuli), and comatose (unresponsive to all stimuli).
What are typical abnormal behaviors associated with CNS disease in horses?
Self-mutilation, head-pressing, compulsive walking, hyperresponsiveness, aggression, and loss of learned behaviors.
What does a head tilt indicate, and which structures are likely involved?
A head tilt often suggests vestibular labyrinth, vestibular nerve, or medulla oblongata/cerebellum involvement.
How does head turning without tilting differ in neurologic implications?
It usually points to forebrain involvement, not vestibular dysfunction.
What is the clinical significance of nystagmus direction in vestibular disease?
Horizontal or arc-shaped nystagmus with the fast phase directed away from the lesion indicates peripheral vestibular disease.
How does proprioceptive deficit manifest in brainstem disease?
Deficits are typically ipsilateral due to affected tracts within the brainstem.
Which cranial nerves are commonly associated with vestibular disease signs?
Cranial nerves VII (facial) and VIII (vestibulocochlear).
What conditions are commonly associated with obtundation and ataxia in horses?
Equine protozoal myeloencephalitis (EPM), West Nile virus, trauma, and neoplasia.
What behavior might indicate cerebellar cortical disease in horses?
Coarse or fine intentional head bobbing and a lack of menace response despite normal vision.
How can examining head orientation provide clues to lesion location?
Head tilt suggests vestibular or cerebellar issues, while horizontal positioning or extended neck may suggest muscular or upper cervical problems.
Describe an abnormal jaw response indicating masticatory muscle paresis.
A dropped jaw with tongue protrusion and easy separation of jaws indicates bilateral paresis.
How is symmetry in temporalis muscle assessed?
How is symmetry in temporalis muscle assessed?
What signs indicate pterygoid muscle atrophy?
Deepness of the supraorbital fossa on the atrophied side.
What is the significance of a blank facial expression with drooping ears and eyelids?
It may indicate obtunded consciousness due to neurologic dysfunction, not systemic disease.
Which signs suggest involvement of the thalamus in neurologic disease?
Behavioral changes, contralateral sensory deficits, and possibly central blindness.
What role does video recording play in a neurologic examination?
It provides a medical record, assists with progressive conditions, and helps with intermittent events like seizures or gait deficits.
Figure 51-2. Atrophy of the muscles of mastication in a horse with equine protozoal myeloencephalitis. Beginning about a month after foaling, this 11-year-old Thoroughbred mare had an insidious onset of ataxia and limb weakness. (A) Six weeks later, ataxia and weakness were worse, especially in the left limbs, and there was obvious atrophy of the masseter and temporalis muscles on the right side. (B) The lower jaw was deviated away from the affected side.
Figure 51-3. Facial paralysis in a horse with polyneuritis equi (neuritis of the cauda equina). Over the previous 2 weeks, this 13-year-old Quarter Horse mare had several exacerbations and remissions of right-sided facial paralysis. Beginning 3 days ago, there were also signs of cauda equina syndrome, including a weak tail and paralysis of the anus.
How does brainstem disease typically affect cranial nerve function?
It can cause multiple cranial nerve deficits, often affecting consciousness, proprioception, and vestibular function.
What sensory condition may occur with injury to the proximal trigeminal nerve?
Hypalgesia, or reduced facial sensation, over one side of the face.
What does weakness or atrophy of the muscles of mastication indicate?
It indicates involvement of the motor division of the trigeminal nerve, its roots, or the trigeminal motor nucleus in the pons.
What additional signs may be observed with trigeminal damage at the level of the pons?
Signs of hindbrain disease, such as obtundation, cranial nerve dysfunction, and proprioceptive deficits.
What are the physical signs of complete unilateral facial paralysis?
Drooping of the ear, upper eyelid (ptosis), lower lip, and asymmetry of external nares.
What reflexes are tested to evaluate facial nerve function?
“Flick” reflexes on the lips, eyes, and ears.
What anatomical structures are implicated if abnormalities of facial tone are present?
The facial nucleus in the medulla oblongata, facial nerve root, or its motor branches.
What does a reduced tear production on the affected side during the Schirmer tear test suggest?
A lesion affecting secretomotor fibers proximal (central) to the middle eaf
What common clinical sign is associated with facial paralysis involving the vestibular system?
Spontaneous nystagmus and head tilt.
What is indicated by reduced or absent responses to a noxious stimulus during sensory testing?
Involvement of the contralateral forebrain.
How is the menace response tested?
By making a threatening gesture toward the eye and observing the blinking response.
What clinical signs may accompany hemifacial hypalgesia due to forebrain disease?
Blindness, obtundation, and abnormal behaviors.
What role does the cerebellum play in the menace response pathway?
It provides essential input to the facial nucleus involved in the response.
What might a decreased menace response indicate regarding the lesion’s location?
It can indicate a contralateral, central lesion in the forebrain.
What is a key sign of long-term facial paralysis affecting the parotidoauricularis muscle?
An obvious subcutaneous depression along the back of the mandible.
How can facial nerve dysfunction affect the cervicofacial reflex?
Its interpretation is influenced by the dysfunction, even though it is not a primary test for facial nerve function.
What are potential nonneurologic signs associated with facial paralysis?
Exposure keratitis or keratoconjunctivitis sicca, and inspiratory stridor during exercise.
What should be observed in normal neonates regarding menace response?
There is typically no menace response, but the horse can still see.
What abnormal behaviors might be observed in a horse with forebrain disease?
Compulsive walking in circles, seizures, and head and neck turn.
How can eyelid paralysis influence the menace response?
It can prevent the response, leading to an abnormal palpebral (eyelid flick) reflex.
What is the primary purpose of examining the pupils in subdued or dim light?
To allow easier appreciation of reflex constriction.
Define anisocoria.
Anisocoria refers to unequal pupillary size.
What does a constricted pupil indicate in veterinary terms?
A constricted pupil is termed miotic.
What is the significance of the dazzle reflex in equine eye examinations?
The dazzle reflex indicates eyelid closure in response to bright light, reflecting functional vision pathways.
Explain the pupillary light reflex (PLR).
The PLR is the immediate constriction of both pupils in response to light directed into one eye.
How does a lesion in the optic nerve affect the direct PLR and menace response?
A lesion in the optic nerve affects both the direct PLR and menace response on the same side.
What clinical signs are associated with mydriasis?
Mydriasis can result from increased sympathetic tone or damage to the oculomotor nerve, leading to fixed and dilated pupils.
Describe Horner syndrome and its association with miosis.
Horner syndrome involves miosis due to loss of sympathetic influence, typically accompanied by other signs like ptosis and enophthalmos.
What does vestibular strabismus indicate in horses?
Vestibular strabismus indicates abnormal eye position, often reflecting vestibular disease.
What is the expected response of the eyeball to a modified corneal reflex test?
The normal response is retraction (adduction) of the eyeball.
Differentiate between physiological nystagmus and spontaneous nystagmus.
Physiological nystagmus occurs with head movement, while spontaneous nystagmus occurs when the head is stationary.
What clinical signs might indicate involvement of the nucleus ambiguus?
Dysphagia, coughing, and signs of aspiration pneumonia may indicate nucleus ambiguus involvement.
Describe the method for assessing swallowing competency in horses.
Assess swallowing competency by noting feed or water returning through the nose and using a nasogastric tube to evaluate swallowing movements.
What are the implications of a horse demonstrating tongue curling towards the normal side?
It indicates unilateral weakness in the tongue muscles.
How can the position of the eyeballs help in diagnosing vestibular disease?
Abnormal positions, like ventral deviation on the side of the lesion, can indicate vestibular disease.
What is the role of the oculomotor nerve in the pupillary light reflex?
The oculomotor nerve mediates the efferent response for pupil constriction in the PLR.
Describe how mydriasis is diagnosed in a horse.
Mydriasis is diagnosed through observation of fixed, dilated pupils and the response to light stimulation.
What is the significance of the slap test in equine examinations?
The slap test assesses for laryngeal paralysis, indicating potential nerve damage
What could cause absent physiologic nystagmus in a horse?
Absent physiologic nystagmus can occur in horses with bilateral vestibular disease.
How does involvement of the hypoglossal nerve affect tongue retraction?
Damage to the hypoglossal nerve can lead to delayed or absent retraction of the tongue, indicating upper motor neuron involvement.
What is the first step in examining a horse’s neck?
Assess muscle mass and look for asymmetries while the horse stands squarely.
What does a firm press on the cranial edge of the cervical transverse processes from C3 to C6 test for?
It tests for a pain response.
What might indicate cervical and/or thoracic pain during the examination?
Inability to lower the neck or the horse advancing one thoracic limb to reach food on the ground.
What condition is often indicated by severe or rapidly developing muscle atrophy?
Denervation, which is a localizing sign.
How is neurogenic muscle atrophy caused?
By damage to the lower motor neuron in the ventral column of the gray matter or associated nerve roots.
Which spinal cord segments are associated with neurogenic atrophy of the thoracic limb musculature?
C6 to T2 spinal cord segments.
What response is expected during the slap test?
slight palpable movement (adduction) of the left arytenoid in response to each slap.
hich reflex provides sensory input to the slap test?
: Sensory nerves and roots from approximately T7 to T11.
What does a diminished cervicofacial reflex indicate?
Interruption of reflex components in the facial nerve, cervical nerves or roots, or local cervical spinal cord segments.
What is tested by the cutaneus trunci reflex?
The responsiveness of the skin to stimulation along the sensory field.
Where does the reflex pathway for the cutaneus trunci reflex lead?
From sensory thoracic nerves to the ipsilateral spinal cord, then rostrally to segments C8 and T1.
What is the expected reaction when the back reflexes are tested?
A brisk extension of the back and pelvis followed quickly by a return to normal posture.
What abnormal reactions might occur during the back reflex test?
Partial collapse in the pelvic limbs, wobbling of the pelvis, or no response.
How can limb strength be assessed in horses?
By observing responses to passive pressure, hopping tests, and resistance to pressure over the pelvis and tail.
What does a horse’s inability to resist sideways pressure during the tail pull indicate?
Possible interruption of the antigravity myotatic reflex pathway.
Which areas of the spinal cord are implicated when cutaneous sensation over the saphenous vein is absent?
The ventral aspect of the shaft of the ilium where the sensory saphenous nerve joins the femoral nerve.
How can spinal cord disease be identified during the examination?
By observing ataxia, weakness in limbs, and changes in gait.
why might the cutaneus trunci reflex not be elicited in some horses?
Due to variations in neck anatomy that affect palpation.
What may be observed in a horse with cervical spinal cord disease during the slap test?
Abnormal adductor responses or bilateral effects if the disease is severe.
What are some associated clinical signs of cervical spinal cord disease beyond ataxia and weakness?
Dysphagia, aspiration pneumonia, and Horner syndrome.
Figure 51-5. Unilateral tongue atrophy in a horse with possible equine protozoal myeloencephalitis. Note the characteristic longitudinal folds on the atrophied (right) side. The tongue intermittently deviated toward the left side when the mouth was held open.
Figure 51-7. Testing for strength: walk backward and pull the horse in counterclockwise circles, then repeat in mirror-image fashion in clockwise circles.
Figure 51-6. Force the horse to hop on each front limb to evaluate limb strength.
Figure 51-8. Gait analysis: pull the horse sideways and backward in tight circles so that it pivots around a point midway between the thoracic and pelvic limbs. Repeat on the right side.
Figure 51-9. Testing the patella reflex in a recumbent horse. The limb is held in a flexed and slightly abducted position, and the skin over the middle patella ligament is struck with a twitch handle.
Figure 51-11. Lumbosacral cerebrospinal fluid collection. The caudal border of the tuber coxae (large dark arrows), the cranial edge of the tuber sacrale (small dark arrows), and the spine of L6 (open arrow) are used as landmarks.
Figure 51-12. Survey radiographs of the neck of a standing normal horse. (A) Fifth cervical vertebra. a, Caudal articular process of C4; b, cranial articular process; c, transverse process (cranial part or ventral tubercle); d, vertebral body; e, dorsal lamina; f, intervertebral disc space; g, vertebral canal. The line shows the sagittal diameter of the vertebral foramen.
Figure 51-12. Survey radiographs of the neck of a standing normal horse. (A) Fifth cervical vertebra. a, Caudal articular process of C4; b, cranial articular process; c, transverse process (cranial part or ventral tubercle); d, vertebral body; e, dorsal lamina; f, intervertebral disc space; g, vertebral canal. The line shows the sagittal diameter of the vertebral foramen. (B) to (F), Five overlapping views of a complete cervical series. Note for this figure: the transverse processes of C6 differ from those of C3 to C5 by presenting an additional ventral process. The caudal part (also called dorsal tubercle) of the transverse processes (most often of C6 but occasionally of other cervical vertebrae as well) can have a separate center of ossification that should not be confused with a fracture. C7 is a relatively short vertebra with usually a small dorsal spinous process and short transverse process that lacks the ventral, cranially facing tubercle that is present in C3 to C6. (
Figure 51-16. Lumbosacral epiduroscopy in the standing horse, looking cranially. Top of the picture is dorsal. A right spinal nerve root (black arrow) passes through the epidural space. Note the epidural fat (white asterisk) and the surface of the dura mater (black asterisk).
Figure 51-14. Cervical myelography: dorsal myelographic column (left of figure), dural diameter (right of figure).
Figure 51-13. Cervical myelographic series in a normal horse. (A) to (C) The neck is in a neutral position. Note that the transverse processes of C6 in this horse do not have the typical ventral extension. (D) Now centered caudally, the neck is in extended position. (E) to (F) Cranial and middle views of the neck in flexed position.
Figure 51-17. Cervical vertebral canal endoscopy. Myeloscopy during withdrawal of the endoscope. Subarachnoid space dorsal to the spinal cord, looking caudally. Top of the picture is dorsal. The arachnoid/dura mater is dorsal (white arrow), partially covered by broken down arachnoid trabeculations (white arrowheads). Ventral, the spinal cord (large black arrow) with blood vessels that are partially enclosed in the delicate pia mater can be seen. A left dorsal nerve root (black arrowheads) is visible.
Figure 51-18. Instruments for the collection of muscle samples. (A) Top: scalpel blade; center: 8-mm skin punch biopsy; bottom: Bergstrom biopsy needle with its components. (B) Double Kelly forceps to be used with one hand to clamp a piece of muscle between the jaws of the forceps. This technique provides a 1.5- by 1.5-cm muscle specimen.
Figure 51-19. (A) The shaved areas depict the region for gluteus medius muscle biopsy, and the black line indicates the site for biopsy of the semimembranosus muscle. The surgical incision required is smaller than the one shown here. (B) Bergstrom biopsy needle for gluteus medius muscle biopsy. The biopsy is performed at about one-half to two-thirds of the distance between the base of the tail and the tuber coxale. Needle is directed 45 to 65 degrees perpendicular to the ground and directed medially to the horse. (C) Area of the sacrocaudalis dorsalis lateralis muscle at the base of the tail.
