Exam 6: Neuro Flashcards
Most critical part of clinical neurology
neuroanatomic diagnosis
No conscious proprioception in pelvic limb, no voluntary movement of pelvic limb, but normal patellar and withdrawal reflexes, thoracic limbs normal: which spinal cord segments?
T3 - L3 spinal segments
Acute Spinal Diseases: most common causes
- Trauma (external)
- Neoplasia
- Myelitis/meningitis
- Intervertebral Disk Disease
- Vascular
Don’t forget…
Look where you localize!!!
Things to note when considering neurological abnormalities:
Look for abnormalities of:
- Posture
- Appearance
What is a hyperkeratotic pad (“Hard Pad”) associated with?
Distemper has been associated w/ hyperkeratotic pad
Physiological causes of Muscle Atrophy
- Disuse (takes time, usually bilateral)
- Neurogenic (can be acute; 3-5 days after damage to a nerve)
- Primary myopathic
Paraspinal Muscle Atrophy
Often caused by discospondylitis
asymmetry of face
1) palpebral fissure differences
2) nasal filtrum deviation
(cranial nerve seven-facial nerve controls this)
opisthotinus
spasm of the muscles causing backward arching of the head, neck, and spine, as in severe tetanus, some kinds of meningitis, and strychnine poisoning.
Decerebrate rigidity
1) opisthotinus
2) extensor rigidity
3) stupor or coma
PATHOGNOMONIC for disease in the midbrain
CLINICAL signs suggest location, not specific disease
(cerebellar disease can look like this but they remain conscious since cerebellum doesn’t involve consciousness. They may do extensor movements intermittently.)
Decerebrate rigidity
Pathognomonic for MIDBRAIN LESION
- rare for animals to recover at this point
- could be heartworm thrombosis, Toxoplasma, FIP
Postural abnormalities
extended or flexed!!
Remember: decerebrate rigidity
Is pathognomonic for midbrain lesion!
But remember tetanus can also look like this. You would want to look immediately for a wound.
But remember spinal cord disease may also disrupt balance between flexors and extensors (i.e. cervical disc problem)
Muscle fibrosis ==> contraction
We can see extensor problems with damage to muscle (i.e. femoral fracture causing fibrosis of quadriceps)
Cushing’s disease and heavily muscled?
Being heavily muscled may cause a stiff stilted short and choppy gait, which is an extensor posture and gait. (Cushing’s disease may cause heavy muscling)
Shiff-Sherrington Posture
1) usually occurs with acute lesions in thoracolumbar area (i.e. fracture of T13-L1 area)
2) front limbs extended, pelvic limbs neutral or slightly flexed (not actively)
Extended Postures
1) neurologic disease (usually central)
2) muscle (skeletal?)
(Also consider tetanus)
Gastrocnemius muscle
Extends hock and is innervated by the sciatic nerve
-may see over flexion of the hock when something is wrong with the gastrocnemius muscle or the sciatic nerve (note if flexion is when they put weight on the limb or not weight on the limb)
Problem with gastrocnemius tendon
1) the superficial digital flexor tendon may be allowed to over-tense the toes
- the toes may be knuckled under and you may see over flexion of the hock at weight-bearing
Gastrocnemius tendon rupture
1) superficial digital flexor over-flexes
- causes knuckling of toes
Cranial tibial muscle
1) flexes the hock
2) is innervated by the sciatic nerve
3) it’s not common to get nerve avulsion with this muscle group
Decreased tone in the pelvic limb
1) indicates damage more likely is present in peripheral nerves
2) sciatic nerve arises from L6, L7, S1, and maybe S2
Fibrotic myopathy
PATHOGNOMONIC GAIT (it's like the only one in vet med neuro!) -The hock turns inward at the height of its elevation
1) semimemnranosus, semitendinosus, and sometimes gracilis muscles become fibrotic and prevent normal movement of the limb
2) German shepherds are over-represented with this disease
3) it’s musculoskeletal disease!! It’s not neurologic disease
4) it likely occurred due to damage of the muscle
Flexed limb postures (when on the ground)
1) neurologic disease (peripheral)
2) muscle (skeletal?)
Flexed limb postures
1) most common pathophysiologic cause: PAIN
2) flexed limb postures are traditionally called “nerve root signature”
If the pelvic limb is affected
DO A RECTAL EXAM
-check for masses etc.
Flexed limb postures (non-weightbearing)
1) PAIN-most common pathophysiologic cause, arising from a structure around the leg
2) neurologic?
3) musculoskeletal?
Ataxia
Lack of an axis
Scoliosis
1) posture of the spine: SIDEWAYS curvature of spine
2) often associated with nervous system problem
- often is in innervation problem to paraspinal muscles, which leads to bone problems in the developing adolescent
Syringomyelia
1) a chronic progressive disease in which longitudinal cavities form in the cervical region of the spinal cord. This characteristically results in wasting of the muscles and a loss of sensation
2) the Cavalier King Charles spaniel have this disease very, very commonly-they are the poster child for this disease!!
Kyphosis
refers to an exaggerated rounding of the back
Ventral neck flexion in the
It is associated with a variety of diseases:
1 electrolyte (potassium) abnormalities
2) hyperthyroidism
3) thiamine deficiencies
4) myasthenia gravis
5) organophosphate toxicities (they also often assume a praying position)
6) a number of other causes..
Short and choppy gait
Usually means one of two things:
1) they are painful
2) they have weakness
What is the tragic facial expression often associated with?
HYPOTHYROIDISM
-often due to muscle weakness
Cranial cruciate ligament rupture
May also cause over-flexion of the stifle
lordosis
Is commonly seen, but usually this is a wasting muscle weakness
1) often associated with Cushing’s disease (hyperadrenocorticiscm)
2) not usually associated with pain
Patient keeping their head down?
It usually indicates there’s pain somewhere (dogs with cervical pain often present with a codified posture and thoracic lumbar area)
Flexure posture with no weight-bearing
Often associated with pain
Flexor posture with weight-bearing
Often associated with musculoskeletal issue
Extensor posture
CNS problem and/or fibrosis of muscle
Head tilt
Vestibular or cerebellar problem
Vestibular or cerebellar problem
Head tilt
-head tilt doesn’t tell you if it’s a central problem or a peripheral problem!!
Gravity
When the central nervous system can’t compensate for gravity, we see clinical signs
-normally the vestibular system is taking care of gravity’s effect on the body
Head turn
1) usually associated with an issue in the brain (usually in the cortex)
2) usually the head turns TOWARD the side of the lesion
Head tilt
Vestibular or cerebellar issue
Head turn
Intracranial issue
Circling
Can be a vestibular problem or can be a cortical problem (sort of like a head turned in action)
-usually is nervous system problem
Which eye is normal?
Dogs and cats tend to follow the bridge of the nose-the eye that DOESN’T follow the bridge of nose, is abnormal
-strabismus (misalignment of the eyes)
Proprioceptive deficits in both thoracic and pelvic limbs
This is likely a central nervous system issue
Positional strabismus
The problem is on the SAME side as the eye deviation
Suspect a structural problem?
Then you must perform a test that analyzes structure!
-I.e. imaging study
Strabismus
Disorder in which the eyes don’t look in exactly the same direction at the same time
Nystagmus
One or both eyes moves quickly, then slowly, then quickly, then slowly
- nystagmus can be horizontal or vertical
- this is the CNS resetting the eyes to their normal position after they drift off
Eye tremor
One or both eyes moves quickly back and forth
Horizontal nystagmus
Can be a CNS or a peripheral nervous system problem
Vertical nystagmus
Usually more associated with the central nervous system problem (i.e. vestibular)
Remember
Clinical signs are NOT pathognomonic for disease, but they help tell you where disease is occurring
often if you put these animals in odd positions (i.e. on back) they may show their nystagmus (if normal they should NOT have nystagmus no matter their position)
Metronidazole toxicity
One of the main side effects of metronidazole is that it can be toxic to the VESTIBULAR SYSTEM!!!
- The sooner that you recognize it, the sooner they can be taken off of metronidazole and the more likely signs will resolve (there are animals that can die from this
- bottom line is, ANY dose of metronidazole CAN be toxic
- it’s metabolized by the liver, so if liver is dysfunctional it can be toxic (be wary of giving it in a patient with a PSS)
Menace response
Tests integration of vision
Anisocoria
Pupils of different sizes
Pupil innervation
1) parasympathetic through cranial nerve 3 stimulates pupil to constrict
2) sympathetic dilates the pupil
Ptosis
Droopy eyelid
Miosis
Constriction of the pupil (sympathetic problem)
Mydriasis
Dilated pupil (parasympathetic problem)
Cranial nerves 3, 4, and 6
The cranial nerves are important for keeping the eye in normal position
Eye deviated laterally
Due to lack of normal muscle tone opposite to the direction the eye is deviating towards(cranial nerve 3 problem-it innervates muscle on the medial aspect of the eye, if damaged eye is pulled lateraly)
Lateral deviation of the eye?
Cranial nerve 3 issue
Medial deviation of the eye?
Cranial nerve 6 problem-it relates the lateral rectus muscle
Rotation of the I?
Cranial nerve 4 problem-it innervates the dorsal oblique muscle
Cross eyed cat?
Common characteristic of Siamese cats, but not “normal”
Horner’s syndrome
1) sympathetic problem with the eye: miotic pupil, prolapse of third eyelid, enopthalmus
2) cattle sympathetic problem with the eye, they may also show dryness of the muzzle on that side of the face
3) horses: they may sweat on the side of the neck that their eye has sympathetic issues with
4) Most Common Thing You See Clinically with Sympathetic Denervation of the Eye Is Miotic Pupil
Sympathetic innervation to pupil
Remember that it travels down the neck before running back up towards the eye
-so it could be damaged near the brain, cervical spine, near the ear, or near the eye, and cause clinical signs in the eye
Palpebral reflex
Involves cranial nerve 5 and 7
-cranial nerve 7 (i.e. facial nerve) also innervates the facial muscles and ocularis muscle around the eye that closes the palpebral fissure
Facial nerve paralysis?
Then you can’t close the palpebral feature!
Cranial nerve 5 (trigeminal)
Innervates the muscles of mastication
Muzzle deviation in the horse
1) normal muscle, with lacking innervation to opposing muscle on the opposite side of the face, causes muzzle deviation
2) deviation is away from the side of the lesion
Muzzle deviation in the dog
1) deviation of the filtrum*-the filtrum points TOWARDS side of the problem!
- Muscles are not as strong as in the horse
2) it could be a chronic fibrosis problem and muscles are stuck in that position, OR it is a hemi-facial spasm
- there is no way to separate these except by blocking the facial nerve and if it goes away it’s a hemi-facial spasm
Temporalis muscle
1) innervated by cranial nerve 5-mandibular branch (trigeminal nerve)
2) if the temporalis muscle decreases in size, there appears a divot on the top of the dogs head
What are the pathophysiological causes of muscle atrophy?
1) disuse
2) neurogenic
3) primary myopathic
Very Acute Muscle Atrophy Is Usually NEUROGENIC (but, don’t rule out a neoplastic cause)
Muscle atrophy clues..
1) is it localized?
2) is it generalized?
Cranial nerve 5
1) it also innervates the cornea sensory
- potential for decreased tearing (cranial nerve 7 also involved with tearing)
- the cornea needs innervation from cranial nerve 5 to maintain integrity
- without cranial nerve 5 the cornea may get ulcerated
you may see a crusty nose on the same side as corneal ulcer due to cranial nerve 5 or 7 nerve damage
Cranial nerve 5-mandibular branch
Bilateral damage may allow the jaw to hang open!
Menace response
Cranial nerve 2 and 7
Palpebral response
Cranial nerve 5 and 7
Most common tumor in the dog brain
Meningioma
Lateral deviation of the tongue?
1) it may be due to atrophied muscle (disuse, neurogenic, primary myopathic)
- cranial nerve 12 ==> Hypoglossal
Look for abnormalities of:
1) movement
2) posture
Body systems necessary for movement
1) musculoskeletal
2) cardiopulmonary
3) nervous system
4) metabolic
Inter-step distance
When both pelvic or thoracic limbs are on the ground, what’s the difference (length) between the two
-i.e. both pelvic limbs compared, or both thoracic limbs compared
Remember
Think pathophysiologically, not etiologically!
Dysfunction of what body systems is associated with abnormalities?
Neurologic?
Musculoskeletal?
Cardiopulmonary/vascular
General metabolic?
UMN
Central nervous system controlling disease
LMN
Peripheral nervous system disease
Hypermetria
Exaggerated flexion
Is it more or less?
I.e. height, overstep, side to side movement
-atrial fibrillation of gait is almost always associated with a CNS problem
More - over movements usually…
= central nervous system disease (UMN disease)***
Irregular foot fall pattern is usually…
Central nervous system disease (UMN disease)
Cerebellum
Does not involve conscious thought
More extension or more flexion during flight…
Usually associated with central nervous system disease (UMN disease)
Degenerative cerebellar problem
- ) More
2. ) Common in Brittany spaniel’s
Sensory neuropathy
This may also sometimes cause MORE… Sensory problem only (i.e. conscious proprioception deficit)
All 4 limbs have MORE?
Suspect CNS/UMN - look cervically or intracranially
