ICVA - International Council for Veterinary Assessment Equine Lameness and Neurology Questions and Answers

Question 1

A 10-year-old Quarter Horse gelding presents with a 2-week history of asymmetric hindlimb ataxia, gluteal muscle atrophy, and a head tilt. The owner reports the signs are slowly progressive. Which of the following diagnostic approaches is considered the gold standard for an antemortem diagnosis of Equine Protozoal Myeloencephalitis (EPM)?

Accepted Answer

Paired serum and CSF antibody testing to demonstrate intrathecal antibody production.

Answer

The most accurate method for diagnosing EPM in a living horse involves comparing antibody levels in both serum and cerebrospinal fluid (CSF). A higher antibody titer in the CSF compared to the serum (a high serum:CSF ratio) indicates that antibodies are being produced within the central nervous system, which is highly suggestive of an active infection. Serum testing alone only indicates exposure to the parasite, not active disease, as a high percentage of healthy horses are seropositive. CSF testing alone can be misleading due to potential blood contamination. While response to treatment is sometimes used, it is not a definitive diagnostic method.

Question 2

A veterinarian is performing a lameness examination on a horse with a right forelimb lameness. The lameness is completely resolved after a palmar digital nerve (PDN) block. Which of the following structures is LEAST likely to be the source of pain?

Accepted Answer

Proximal interphalangeal (pastern) joint

Answer

A palmar digital nerve (PDN) block, or heel block, desensitizes the palmar third to one-half of the foot. This includes the navicular bone, navicular bursa, digital cushion, sole, frog, and portions of the coffin joint and deep digital flexor tendon. The proximal interphalangeal (pastern) joint is innervated by more proximal nerves and would not be fully desensitized by a PDN block. Pain originating from the pastern joint would typically be resolved with a more proximal block, such as an abaxial sesamoid nerve block.

Question 3

A 2-year-old Thoroughbred colt presents with symmetric hindlimb ataxia that is worse when the horse's head is elevated. The colt is bright and alert with a normal appetite. Radiographs of the cervical spine reveal narrowing of the vertebral canal at C3-C4. What is the most likely diagnosis?

Accepted Answer

Cervical Vertebral Stenotic Myelopathy (CVSM)

Answer

Cervical Vertebral Stenotic Myelopathy (CVSM), also known as Wobbler Syndrome, is a common cause of symmetric ataxia in young, rapidly growing horses, particularly Thoroughbreds and Quarter Horses. The clinical signs, including symmetric hindlimb ataxia that worsens with neck extension (head elevation), are classic for this condition. The diagnosis is supported by imaging, such as radiographs or a myelogram, which demonstrates narrowing of the spinal canal and subsequent spinal cord compression.

Question 4

Which of the following clinical signs is most characteristic of stringhalt in a horse?

Accepted Answer

Involuntary, spasmodic hyperflexion of one or both hindlimbs during the walk.

Answer

Stringhalt is a neuromuscular condition characterized by a sudden, involuntary, and exaggerated upward flexion of one or both hindlimbs during movement, most notably at the walk. The leg is quickly snapped toward the abdomen and then slapped back down on the ground. This is distinct from shivers, which is more often seen when the horse is backing up and involves abduction of the limb. Symmetric ataxia is more typical of spinal cord disease, and progressive muscle atrophy is seen in conditions like EMND or EPM.

Question 5

A 5-year-old Warmblood gelding used for dressage is presented for poor performance and a subtle right hindlimb lameness. The lameness is not obvious on a straight line but is exacerbated when the horse is lunged on a hard surface with the affected limb to the inside. A low four-point nerve block fails to improve the lameness, but a subsequent tibial and peroneal nerve block significantly improves the gait. Pain is most likely originating from which region?

Accepted Answer

The hock (tarsus) or structures distal to it

Answer

A low four-point block desensitizes the fetlock and all structures distal to it. Since the lameness did not improve with this block, the source of pain is located more proximally. The tibial and peroneal nerves provide sensation to the hock and the distal limb. A positive response to a tibial and peroneal nerve block after a negative low four-point block localizes the source of pain to the hock region. If the lameness improved only after the tibial nerve block, the proximal suspensory ligament would be a primary suspect.

(ICVA) International Council for Veterinary Assessment Practice Test

(ICVA) International Council for Veterinary Assessment Practice Test

ICVA - International Council for Veterinary Assessment Equine Lameness and Neurology Questions and Answers