Page 766 - Clinical Small Animal Internal Medicine

734 Section 8 Neurologic Disease

correct. Why then are they useful? First, testing postural relaxes and extends for a brief period, creating a tremor.
VetBooks.ir reactions acts as a screen for detecting abnormalities in Grades 2, 3, and 4 occur with UMN lesions. This is the
most reliable tendon reflex and determines the integrity
the nervous system. Abnormal responses will be the first
clinical sign of any progressive lesion in any part of the
segments. Always check the patellar reflexes in both
central or peripheral nervous system that is involved in of the femoral nerve and the L4, L5, and L6 spinal cord
limb movement. One or more of these postural reactions limbs while in both recumbencies because, in normal
may be abnormal before any detectable abnormality in dogs, it will occasionally be absent in one position and
the gait is observed. Second, their importance in local- not the other. We have no explanation for this phenom-
izing lesions is dependent on the results of the rest of enon. Also recall that, in dogs 10 years of age or older,
the neurologic examination. If the gait is normal in the one or both patellar reflexes may be absent with no other
environment of your examination and one or more of neurologic signs present. The presence of normal tone
the postural reactions are abnormal in the limbs on one and the lack of any atrophy suggest that the basis for
side of the body, a contralateral prosencephalic lesion is this sign is on the sensory side of the reflex arc, which
strongly suggested. This test is the most useful of the may involve an age‐related sensory neuropathy.
three clinical tests that we use for prosencephalic disorders. However, this suggestion has not been proven. The
If you have a patient with clinical signs of a unilateral patellar reflex is the most reliable tendon reflex in our
vestibular system disorder with a normal gait but the examination of a patient.
postural reactions are abnormal, then the lesion is in the Other tendon or muscle reflexes elicited by striking the
central components of the vestibular system. tendon (gastrocnemius muscle – tibial nerve) or muscle
Remember to use terminology that all clinicians can (cranial tibial muscle – fibular nerve) are of limited use
understand. Lesions that affect the UMN pathways also because they are not present in all normal small animals
affect the GP pathways; thus when you describe a gait and some occur in denervated muscle. I do not consistently
abnormality as paraparesis, also include pelvic limb perform these reflexes. Be sure to test the patellar reflexes
ataxia. Use tetraparesis and ataxia for C1–C5 spinal before the withdrawal reflexes because the latter require
cord lesions and hemiparesis and ataxia for unilateral a noxious stimulus that may upset your patient.
C1–C5 spinal cord lesions that affect the gait. If the gait The withdrawal‐flexor reflex is evaluated in both pelvic
is normal and the postural reactions are abnormal on limbs. This reflex requires an adequate noxious stimulus
one side, describe it that way, and do not refer to this that differs between individual patients. A pin may be
abnormality as hemiparesis. Be sure your reader can adequate in many cats but not in many dogs. I prefer
clearly understand what you have observed. using tissue forceps because the degree of compression
can be adjusted to the individual patient. Compress the
skin at the base of the third phalanx of a digit with enough
Muscle Tone and Size, and Spinal Reflexes
pressure to elicit the reflex and usually a slight conscious
In small animals, examination of these features is per- response in a normal patient. By increasing the com-
formed in the recumbent patient that is gently restrained pression of the digit, the stimulus becomes sufficiently
by an assistant. You can conduct this test unassisted in a noxious to elicit nociception. Your digital pressure is
cooperative patient by gently kneeling on the patient’s sometimes sufficient, but a pair of tissue forceps is usually
neck to hold it in lateral recumbency. For cats, toy breeds, more reliable. Remember that this noxious stimulus tests
and puppies, you might want to sit on the floor with your both the spinal nerve reflex and the pathways in the CNS
back against a wall and your knees held together and for nociception. You can have a reflex loss without loss of
flexed. Place the patient with its back resting against your nociception; therefore you must use care in the amount of
thighs. This position is also useful for the cranial nerve pressure you apply to avoid excessive discomfort to the
examination. patient and injury to you by the patient.
Flex and extend the limbs on the nonrecumbent side to This withdrawal reflex is a more complex reflex. The
assess muscle tone, and palpate the muscles again for any sensory neurons tested depend on the digit being tested
indication of atrophy. For the patellar reflex, hold the or the autonomous or cutaneous zone that you select
pelvic limb in partial flexion, and, with the limb as for this noxious stimulus. Compression of the first
relaxed as possible, lightly strike the patellar ligament digit stimulates receptors innervated by the saphenous
with a human pediatric patellar hammer or any blunt nerve (femoral nerve, spinal cord segments L4–L6).
instrument. The response is a brisk extension of the Compression of digits 2–5 stimulates receptors innervated
stifle. This response can be graded as 2 for normal, 1 for by the sciatic nerve (tibial nerve on the plantar surface and
depressed, and 0 for absent; grade 3 is hyperactive, and fibular nerve on the dorsal surface). The motor response
grade 4 is clonic. A clonic reflex is one in which, after the involves primarily the sciatic nerve in the pelvic limb,
response to a single stimulus, the stifle repeatedly rapidly with caudal thigh muscular branches responsible for