26.neuro_exam Flashcards
6 parts of a neuro exam
- sensorium and behavior2. posture and gait3. postural reactions4. spinal reflexes, muscle mass, muscle tone5. cranial nerves6. cutaneous sensation
obtunded vs stupor vs coma
—obtunded—decreased arousal in response to touch/voicedepression—stupor—arousable to vigorous stimuli but response is incomplete or inadequate–coma—sustained unresponsiveness to stimuli
alteration in sensorium is typically due to what disturbances
- disturbance in the ascending reticular activating system2. disturbance in cerebrum3. disturbance in the limbic system (cerebrum/brainstem–diencephalon)suggests intracranial disease
define lower motor unit
- ventral horn cell2. axons of peripheral nervous system3. NMJ4. innervated muscle
decerebrate vs decerebellate rigidity
both indicate disruption of descending inhibitory influence on the nerves going to extensor musclesdecerebrate—opisthotonous, mentation changes/menace, rigid neck x 4 limbs—-indicate midbrain or rostral cerebellar lesiondecerebellate—opisthotonous, do not always affect mentation, rigid neck x 4 limbs but hind limbs FLEXED—-indicate SEVERE cerebellar lesion
area of nervous system leading to gait abnormalities
midbrainstem and caudal (caudal brainstem, spinal cord, peripheral nerve)ataxia (vestibular, cerebellar, proprioception)weakness (can be UMN or LMN)lameness (LMN or ortho)
T/Fchronic structural changes in prosencephalon do NOT result in obvious gait abN
TRUEchronic structural changes in prosencephalon do NOT result in obvious gait abN
variation in LMN paresis/gait
mild-moderate LMN dz: ambulatory with short, choppy, stilted gaitSevere LMN dz: non ambulatory or tetraplegicnot usually ataxic bc GP pathways are unaffected
modified franked scoring
0 plegia with no deep pain1 plegia with no superficial pain2 plegia with nociception intact3 nonambulatory paresis4 ambulatory paresis , ataxic5 spinal hyperesthesia only
variation in UMN paresis/gait
long strided, spastic gaitgeneral proprioceptive ataxia
why is it difficult to separate general proprioceptive ataxia vs UMN dz
adjacent pathway anatomicallytherefore it is difficult to separate the effect on gait caused by dysfunction of descending UMN path vs dysfunction of ascending proprioceptive pathwaysdogs w only proprioceptive ataxia are assumed to have UMN dz
T/Fanimals with LMN dz/neuromuscular dz actually have NORMAL postural rxn
TRUEanimals with LMN dz/neuromuscular dz actually have NORMAL postural runbecause a LACK of disruption of general ascending proprioceptive pathways. Therefore, rely on spinal reflexes to dx
what do normal postural run depend on
intact conscious AND UNCONSCIOUS proprioception and intact UMN and LMNSENSORY –>DORSAL HORN (IPSILATERAL SPINAL CORD TO MIDBRAIN Unconscious Proprioception, CONTRALAT PROESNCEPHLAON Conscious Proprioception)
T/Fa dog with NM dz (ie. myasthenia gravis) may still have proprioceptive deficits
TRUEeven though the lesion is NOT in the proprioceptive pathway the dog is too weak to return paw to normal anatomic position
most reliable spinal reflexes
patellar withdrawal
patellar reflex
L4-L6femoral nstifle extension(maybe abN in older dogs without signs of neuro dz)
the finding of an absent or hyporeflexia spinal reflex indicates a problem where?
- afferent limb2. efferent limb3. spinal cord segment involved in reflex arc
the finding of a hyper reflexive spinal reflex indicates a problem where?
lesion cranial to the spinal cord segment containing the reflex arc
biceps and triceps spinal reflex
biceps reflex–musculocutaneous n (C6-8)–slight flexion of elbow, and movement over muscletriceps reflex–radial n (C7-T2)–slight extension of elbow, contraction of triceps
pelvic vs thoracic withdrawal spinal reflex
pelvic withdraw–sciatic n (L6-S1)thoracic withdraw–brachial plexus n (C6-T2)(S-S)-M-A-R-M-UComplete flexion of all joints!!
stance of dogs with sciatic nerve injury
PLANTIGRADE due to tibial nerve dysfunction (which is a branch of sciatic, courses medially to innervate gastrocnemius muscle)PAW MISPLACED ONTO DORSUM due to peroneal nerve dysfunction (which is a branch of sciatic, courses laterally to cranial tibialis muscle)LMN dz BUT pelvic limb is not usually short strided but rather exaggerated and “flings” foot forwardlimb will be able to support weight if femoral nerve is intact bc stifle can be extended to bear weight; hip is flexed
where do the median and ulnar nerves innervate
PALMAR
where does the ulnar nerve innervate
LATERAL aspect of DIGIT 5
where does radial nerve innervate
dorsum of footcranial and lateral antebrachium
where do ulnar and musculocutaneous nerves innervate
caudal and medial antebrachium (ulnar n) and brachium (musculocutaneous n )
where do perineal and tibial branches of the sciatic nerve innervate
dorsal (peroneal n ) and plantar (tibial n)
where does the saphenous branch of femoral nerve innervate
medial aspect of pelvic limb (digit 1)in some patients, innervation by the saphenous nerve is not present distally.
perineal spinal reflex
sacral and caudal branches of pudendal nerveS1-S3
Cutaneous trunci reflex
sensory input via dermatomes lateral thoracic nerve C8-T1—>cutaneous trunci musclereflex is preserved for 1-2 vertebral bodies caudal to the level of the spinal cord lesion
cranial nerves
ooottafvgvah pg 332olfactoryopticoculomotortrochleartrigeminalabducensfacialvestibularglossopharyngealvagus accessoryhypoglossal
menace reflex
most reliable for visiontests 2 optic, 7 fascial innervation orbicularis oculi mlearned response 10-12 wk of age
why does an indirect PLR occur
PLR tests 2 optic, 3 oculomotor nindirect/consensual response occurs bc crossing over fibers at optic chasm and pretectal nuclei to stimulate parasympathetic oculomotor nerve and iris muscle–> constriction of pupil
horners syndrome
loss of sympathetic innervation to the eye1. ptosis2, third eyelid elevation3. miosis4. enophthalmos
course of autonomic nervous system four sympathetic fibers
preganglionic neuron–CNS (throughout TL spinal cord, join vagus/vagosympathetic trunk,ascend in sheath to cranial cervical ganglion)post ganglionic neuron–PNS (synapse at CC ganglion–near bullae, go to cranium via ophthalmic branch of trigeminal n to innervate muscle)effector muscle (muscle innervated dilator muscle of the pupil in the iris)
ventrolateral strabismusmedial strabismuseyeball extorsion with CN dysfunction
ventrolateral strabismus–oculomotor n dysfunction (3)medial strabismus–abducens n dysfunction (6)eyeball extorsion–trochlear n dysfunction (4)trochlear dysfunction in cats also displays itself as lateral rotation of the dorsal aspect of the pupil
palpebral reflex
5 trigeminal sensory (branches ophthalmic medially maxillary lateral)7 facial motor (branch–palpebral)
trigeminal sensory function is tested with
nasal sensation 1. ipsilateral branch of ophthalmic and maxillary2. nociceptive path to contralateral thalamus / cortex
what nerves control the GAG reflex
glossopharyngealvagushypoglossal
how many spinal cord segments C, T, L, S
cervical 8thoracic 13lumbar 7sacral 3at least 2 caudal coccygealC1-5 C6-T2 (cervicothoracic intumescence) T3-L3 L4-S3 (lumbosacral intumescence)
typical gait for C6-T2 lesions
2 engine gaitthoracic limbs–short choppy (LMN)pelvic limbs–long strides (UMN) with GP ataxia
when is schiff-sherrington syndrome seen
peracute T3-L3 lesionsmarked increased extensor tone in thoracic limbsdue to disruption in ascending inhibitory axons arising from interneurons
describe spinal shock
may occur as T3-L3 lesions in which pelvic limbs display LMN signsdue to transient disconnection btwn the facilitatory descending UMN that modulate function of LMN of the LS intumescence and the spinal neurons
NM or LMN diseases
localized to NMJ, nerves (neuropathy) or muscles (myopathy); can be focal, multifocal, or diffusemay need ancillary testingCK, AST, electrolytesTick borne disease panelsTensilon testingAch Ab titerNerve/Muscle bxEMG
