Lecture 20: Neurologic Exam

what is the most important tool in clinical neurology?

neurologic exam

goals of neurologic exam

• nervous system disease present

• recognize/interpret abnormal signs

• localize lesion

• assess severity of dysfunction

• differential diagnosis

• tentative prognosis

indications of neurologic issues include changes in

• behavior/attitude/onset of seizures

• balance

• gait

• strength/endurance

• muscle tone/symmetry

clinical neurology

• neuroanatomic diagnosis > etiologic diagnosis

• attempt to have single lesion → multifocal or diffuse nervous system disease possible

• localization → differentials → diagnostic plan

history for neurologic exam

• acute vs chronic

• static, improving, progressive

observation of neurologic exam includes

mentation, posture, gait

mentation

• normal (bright, alert, responsive)

• depression/dull → conscious but inactive, usually sick

• obtunded → sleeps when undisturbed

• stupor → touch, noise does not cause arousal; only responds to strong stimuli such as pain

• coma → state of unconsciousness, cannot be awakened even with painful stimulus

• demented/inappropriate

normal posture coordinated by motor responses to

• sensory inputs from receptors in limbs and body

• visual system

• vestibular system

abnormal postures

wide-based stance, leaning, head tilt, schiff-sherrington posture, decerebrate rigidity

increased muscle tone (usually extensors) =

sign of UMN disease

decreased muscle tone =

often associated with LMN lesions

locomotion

• basal nuclei (and motor cortex)

• cerebellum

• vestibular system

• spinal cord

• peripheral nerves and muscles

forebrain lesions

• rarely cause gait abnormality

• minimal to no ataxia or weakness

if gait is affected then

there’s a problem in midbrain or caudally

gait evaluation

• leashed or unleashed

• non-slippery surface

• walk/run

• observe from all sides

• breed differences

ataxia

incoordination of limb movements

paresis

inability to support weight or generate gait; could be from UMN or LMN dz

plegia

complete loss of voluntary motor function

monoparesis/plegia

weakness/paralysis of a single limb

hemiparesis/plegia

weakness/paralysis involving the thoracic and pelvic limb on same side of body

paraparesis/plegia

weakness/paralysis of both rear (pelvic) limbs

what is not a localizing sign by itself?

circling

circling

• animal with forebrain lesion → wide circles

• animal with vestibular dysfunction → tight circles, head tilt usually present

• animals usually circle toward lesion

3 forms of ataxia

• vestibular ataxia

• cerebellar ataxia

• proprioceptive ataxia

vestibular ataxia

• results from loss of orientation of head/neck/body/limbs to each other

• tendency to drift, lean, fall, or roll

cerebellar ataxia

• loss of coordinating input

• often hypermetric gait with overstepping

• may also see intention tremor or truncal sway

proprioceptive ataxia

• disruption of ascending proprioceptive fibers

• spatial information fails to reach the brain

• limbs crossing over, scuffing digits, standing on dorsum of paw, delay in protraction phase

postural reactions

• complex responses that maintain normal, upright body position

• does not specifically localize a lesion

why should you do postural reactions?

• good screen for abnormalities in nervous system

• often first abnormality noticed

• assess for asymmetry

• recognize dog vs cat differences

postural reactions require all parts of the nervous system which includes

• sensory systems

• spinal cord

• cortical integration (somatosensory cortex)

• motor system (UMN and LMN)

• neuromuscular jxn

true or false: postural reactions are only a test of conscious proprioception.

true

what are the types of postural reactions to test?

• proprioceptive positioning (paw placement test)

• placing (tactile)

• placing (visual)

• hopping → hemiwalking

• extensor postural thrust

• wheelbarrowing

hemiwalking

• used in place of hopping in large/heavy animals

• stand to one side → pick up forelimb from behind carpus or from in cubital joint, pick up rear limb from behind stifle

• take several steps to the side

• rear limb will be slightly slower than forelimb

spinal reflexes are independent of

higher brain centers

spinal reflexes evaluate

• components of reflex arc (sensory and motor) → the integrity of the spinal cord segments

• influence of descending UMN pathways on arc

• helps us localize spinal lesions

myotatic (stretch) reflexes are

monosynaptic

flexor (withdrawal) reflexes are

multisynaptic

spinal reflex only

• does not requite any activation of brain

• does not necessarily indicate patient can feel pain

withdrawal reflexes

• most reliable forelimb reflex

• most reliable sciatic reflex

• reflex intact even with cord transection

UMN signs

• increased muscle tone

• normal to hyperreflexia

LMN signs

• flaccid muscle tone

• decreased to absent reflexes

tips for spinal reflexes

• perform with animal in lateral recumbency

• pelvic limb first, then thoracic

• myotatic reflexes first, then flexor

• do one side first, then flip animal

patellar reflex

• strike patellar ligament

• normal response → single, quick extension of stifle

• nerve evaluated → femoral (L4-6)

withdrawal (flexor) reflex in pelvic limb

• firm (least noxious) stimulus applied to the toe

• normal response → flexion of entire limb (hip, stifle, hock)

• nerve evaluated → sciatic (sensory and motor), common fibular and tibial

• cord segments involved → L6, L7, S1, S2

withdrawal (flexor) reflex in forelimb

• same as pelvic limb

• normal response → flexion of entire limb

• nerves tested → axillary, musculocutaneous, median, ulnar, radial

• cord segments involved → C6, C7, C8, T1, T2

cutaneous trunci reflex

• use hemostats and gently grasp skin over dorsum; proceed caudal to cranial

• normal response → skin twitch bilaterally

• very long spinal reflex

• synapse at C8-T1 spinal cord segments

• a cut-off suggests lesion is 2-4 spinal cord segments cranial

perineal (anal) reflex

• light stimulation of perineum with forceps

• squeeze penis or vulva

• normal response → contraction of anal sphincter muscle, flexion of tail

• nerve evaluated → pudendal (S1, S2, S3), perineal (S1, S2, S3)

what cranial nerves are not routinely tested?

CN I and XI

cranial nerves

• most are reflex arcs

• some are responses → implication → requires cortex (menace response, nasal sensation)

menace response

• move hand toward one eye (avoid wind) while opposite eye covered

• normal response is blink (± move head/neck)

• learned response → absent in puppies/kittens

• requires CN II, VII (also cerebellum)

• requires contralateral cortical input

what cranial nerves are involved in menace response?

II and VII

palpebral reflex

• medial canthus

• lateral canthus (less reliable)

• afferent → CN V (trigeminal)

• efferent → CN VII (facial)

what cranial nerves are involved in the palpebral reflex?

V and VII

the three branches of trigeminal nerve are

maxillary, ophthalmic, mandibular

all branches of trigeminal nerve have

sensory (GSA)

mandibular branch of trigeminal nerve has

motor (GSE)

jaw tone from trigeminal nerve

• lesions may cause atrophy of temporalis/masseter muscles

• lesions may cause loss of jaw tone, dropped jaw (bilateral)

facial nerve

• CN VII

• controls muscles of facial expression

• loss causes → wide palpebral fissure, drooping lips/face, immobile ear, deviation of nose

nasal sensation from trigeminal nerve

ophthalmic nn (± maxillary nn)

pupillary light reflex (PLR)

• afferent → CN II (optic nn)

• efferent _> CN III (oculomotor nn)

• assessment of pupil size and symmetry

the pupillary light reflex involves which cranial nerves?

II and III

swinging light test

• direct PLR = what’s happening in the ipsilateral eye

• indirect/consensual PLR = what’s going on in the opposite eye

physiological nystagmus

• doll’s eye movement, oculocephalic reflex, oculovestibular reflex

• a slow phase to the movement, and a fast phase

• afferent → CN VIII

• efferent → CN III, IV, and VI

what cranial nerves are involved in physiological nystagmus?

VIII, III, IV, and VI

abnormal nystagmus

• spontaneous (resting)

• positional (inducible)

• orientation → horizontal, rotary, vertical

• direction of the fast phase

gag reflex

• afferent → IX, X

• efferent → IX, X, (XI), (XII)

• subjective

• difficult to determine lateralization

tongue

• CN XII (hypoglossal n)

• GSE (motor)

hyperesthesia

increased sensitivity to stimulation

spinal palpation

• perform from caudal to cranial

• vertebral column (start at L7)

• squeeze transverse processes

• press each spinous or transverse process firmly

• gently flex and extend neck

sensation will already be evaluated in neuro exam because of

• cranial nerves

• spinal reflexes

• proprioceptive positioning

• spinal palpation

sensation should be performed only

if needed and always last

nociception definition

perception of noxious afferent information

nociception

• often difficult to differentiate between superficial an deep pain perception

• affected by demeanor, pain threshold

• not necessary in most cases

nociception test

• use least noxious stimuli as possible

• fingers before hemostats

• skin/webbing between toes, nailbed, or last digit

normal response indicating deep pain perception

• withdrawal of limb (unless LMN location)

• behavioral response → anxiety, vocalization, attempt to escape

withdrawal of limb only does not indicate

pain perception

what should you perform for a neuro exam if you are in a hurry?

• mentation

• paw replacement

• menace response

what is the goal of neurologic exam?

lesion localization