Neurology- Spinal Nerves/Cord Lesions/Reflexes Flashcards
How many spinal nerves are there?
31 pairs
8 cervical
12 thoracic
5 lumbar
5sacral
1 coccygeal
Nerves C1-C7 exist above the corresponding vertebra but since there are only 7 cervical vertebrae and 8 cervical nerves, Nerve C8 exits below vertebra C7 and all thoracic, lumbar, and sacral nerves exit below their respective vertebrae
What happens in vertebral disc herniation?
the nucleus pulposus (soft central disc) herniates through the annulus fibrosus
What is the most common spot for vertebral disc herniation?
posterolaterally at L4-L5 or L5-S1
Where does th spinal cord end caudually in adults?
L1-L2
The subarachnoid space (which contains the CSF) extends to the lower border of S2 vertebra and a LP is usually performed between L3-L4 or L4-L5 at the level of the cauda equina
Spinal cord and associated tracts pg 469
What does the dorsal column consist of? What does it do?
fasciculus gracilis (lower legs, and body)
fasciculus cuneatus (upper body and arms)
What does the lateral spinothalamic tract do?
part of the ascending pathways that relay pain and temperature sensory to the brain
What does the anterior spinothalamic tract do?
part of the ascending pathways that relay crude touch and pressure to the brain
What does the lateral and anterior corticospinal tracts do?
motor output as part of descending pathways
Again, the dorsal column is involved in ascending relay of pressure, vibration, fine touch, and proprioception. Describe the path of the dorsal column sensory relay?
1st order neuron: sensory nerve ending in the periphery with a cell body in the DRG that sends an axon into the spinal cord and ascends ipsilateraly in the dorsal column
synapse 1: ipslilateral nucleus cuneatus or graculus (medulla)
2nd order neuron: deccusates in medulla and ascends contralaterally in the medial meniscus
synapse 2: VPL (thalamus)
3rd order neuron: sensory cortex
Again, the spinothalamic tract is involved in ascending relay of pain and temp (lateral) and crude touch and pressure (anterior). Describe the path of the spintothalamic tract sensory relay?
1st order neuron: sensory nerve ending (Adelta and C fibers) with cell body in the DRG and enters the spinal cord
synapse 1: ipsilaterl gray matter in the spinal cord
2nd order neuron: decussates at the anterior white commissure and ascends contralaterally
synpase 2: VPL
3rd order neuron: sensory cortex
Again, the lateral corticospinal tract is involved in DEcending relay of voluntary movement of contralateral limbs. Describe this path.
1st order neuron: UMN with cell body in the primary motor cortex that descends ipsilaterally through the internal capsule. Most fibers decussate at the caudal medulla (pyramidal decussation) and descends contralaterally
synapse 1: cell body of anterior horn (spinal cord)
2nd order neuron: LMN leaves the spinal cord
synapse 2: NMJ
Weakness would be a sign of: UMN or LMN lesion?
both
Atrophy would be a sign of: UMN or LMN lesion?
LMN
Fasciculations would be a sign of: UMN or LMN lesion?
LMN
How are reflexes and tone affected by UMN or LMN lesions?
UMN: both increased
LMN: both decreased
A positive Babinski sign, clasp knife spasticity, and spastic paralysis would be a sign of: UMN or LMN lesion?
UMN only
NOTE: a positive Babinskin sign is normal in infants
Flacid paralysis would be a sign of: UMN or LMN lesion?
LMN only
What diseases are caused by disease of the anterior horns?
poliomyelitis and spinal muscular atrophy (Werdnig-Hoffmann disease)
LMN lesions only; flaccid paralysis
What is poliomyelitis?
Poliomyelitis, often called polio or infantile paralysis, is an infectious disease caused by the poliovirus. In about 0.5% of cases there is muscle weakness resulting in an inability to move.[1] This can occur over a few hours to few days.[1][2] The weakness most often involves the legs but may less commonly involve the muscles of the head, neck and diaphragm.
Many but not all people fully recover. In those with muscle weakness about 2% to 5% of children and 15% to 30% of adults die. Another 25% of people have minor symptoms such as fever and a sore throat and up to 5% have headache, neck stiffness and pains in the arms and legs. These people are usually back to normal within one or two weeks.
In up to 70% of infections there are no symptoms.
Years after recovery post-polio syndrome may occur, with a slow development of muscle weakness similar to that which the person had during the initial infection
What causes MS?
demyelination of mostly white matters in the cervical region
Disease of the dorsal columns causes/or is caused by what diseases?
tabes dorsalis
can be caused by vitamin B12 deficiency
What is tabes dorsalis?
a sequelae of teritary syphillis resulting from demyelination of the dorsal columns and roote causing impaired sensation and proprioception, and progressive sensory ataxia (inability to sense or feel the legs leading to poor coordination)
How is poliovirus spread?
fecal - oral
How does poliovirus behave in the body?
It replicates in the oropharynx and small intestine before spreading via bloodstream to the CNS.
Infection causes destruction of cells in the anterior horn of the spinal cord leading to LMN death
How does polio present?
With classic signs of an LMN lesion: weakness, hypotonia, flaccid paralysis, hyporeflexia, and msucle atrophy
Signs of infection as well: fever, HA, nausea, etc.
How does polio present in labs?
CSF with elevated WBCs and slight protein increase (with no change in CSF glucose)
What is Spinal muscular atrophy (Werdnig Hoffmann disease)?
congenital degeneraiton of the anterior horns of the spinal cord due to a LMN lesion
How does Spinal muscular atrophy (Werdnig Hoffmann disease) present?
“floppy baby” with marked hypotonia and tongue fasciculations. Infantile type has a median age of death of 7 months
What is the MOI of Spinal muscular atrophy (Werdnig Hoffmann disease)?
AR
What causes Friedrich ataxia?
AR trinucleotide repeat disease (GAA) on chromosome 9 in the gene that encodes frataxin (an iron binding protein) leads to mitochondrial impairment
How does Friedrich ataxia present?
degeneraiton of multiple spinal cord tracts leads to muscle weakness and loss DTRs, vibratory sense, and proprioception
Kyphosclosiosis (below)
Staggering gait, frequent falling, nystagmus, dysarthria, pes cavus, and hammer toes
What is this?
pes cavus, seen in Friechreich ataxia
What else is common in Friedreich ataxia?
diabetes mellitus
hypertrophic cardiomyopathy (cause of death)
What is Brown-Sequard syndrome?
Hemisection of the spinal cord presenting as:
- ipsilateral UMN signs below the level of lesion (due to corticospinal tract damage)
- ipsilateral loss of tactile, vibration, and proprioception sense below the level of the lesion (due to dorsal column damage)
- contralateral pain and temp loss below the lesion level due to spinothalamic tract damage
- ipsilateal loss of all sensation at the level of lesion
- ipsilateral LMN signs (e.g. flaccid paralysis) at the level of the lesion
Where is sympathetic output from the spinal cord housed?
intemeidtae horn at levels T1-L2/L3
Dermatone landmarks
C2: posterior half of a skull cap
C3: brim of turtle neck
C4: brim of t-shirt
T4: nipple
T7: xyphoid process
T10: umbilicus
L1: inguinal ligmant
L4: kneecaps are included
S2-S4: rection and sensation of penile and anal zones
Diaphragm and gallbladder pain refer where?
right shoulder via the phrenic nerve
Bicep reflex tests what nerve root? Tricep? Patella? Achilles?
Biceps: C5
triceps: C7
Patella: L4
Achilles: S1
Tetsicle reflex tests what nerve root? Anal wink?
L1,L2 (cremaster reflex)
Anal winking: S3, S4
What are ‘primitive’ reflexes?
reflexes present in a healthy infant that dissappear within the 1st year of life and are absent in a neurologically intact adult.
The primitive reflexes are inhibited by a mature/developing frontal lobe and may reemerge in adults with frontal lobe lesions
What are the primitive reflexes?
moro reflex
rooting reflex
sucking reflex
palmar and planat reflexes
galant reflex
What is a moro reflex? Rooting?
“hang on for life” reflex- abduct/extend arms when startled and then draw together
Rooting: movement of ehat toward one side if the check or mouth stroked (nipple seeking)
What is a sucking reflex? Palmar?
uscking repsonse when the roof of mouth is touched
Palmar: curling of fingers if the palm is stroked
What is a plantar reflex? Galant?
Plantar: dorsiflexion of the large toe and fanning of other toes with plantar stimulation (this is called a Babinski sign when present in adults, and signifies an UMN lesion)
Galant: stroking along one side of the spine while a newborn is in ventral suspension (face down) causes lateral flexion of the lower body toward the stimulated side
Ventral Brainstem
Dorsal brainstem
What is the role of the superior colliculi?
conjugate vertical gaze center
Inferior: auditory center
What is Parinaud syndrome?
paralysis of conjugate vertical gaze due to lesion in the superior colliculi (e.g. stroke, hydrocephalus, pinealoma)
Where are most CN nuclei located?
tegmentium portion of the brain stem (between dorsal and ventrl portions)
lateral nuclei (aLar plate)- sulcus limitans- medial nuclei (motor- basal plate)
Which CN nuclei are located in the midbrain?
III, IV
Which CN nuclei are located in the pons?
V, VI, VII, VIII
Which CN nuclei are located in the medulla?
IX, X, XII
Which CN nuclei are located in the spinal cord?
XI
What does CN I do?
olfactory- smell (only CN without thalamic relay to the cortex)
Sensory and passes through the cribriform plate
What does CN II do?
optic- sight
Sensory
What does CN III do?
Oculomotor - eye movement (SR, IR, MR, IO), pupillary constriction (Sphincter pupillae: Edinger-Westphal nucleus, muscarinic receptors), accommodation, eyelid opening (levator palpabrae)
Motor
What does CN IV do?
Trochlear- eye movement (SO)
Motor
What does CN V do?
trigeminal- mastication, facial sensation (ophthalmic, maxillary, and madibular divisions), somatosensation from anterior 2/3 of tongue
Both
What does CN VI do?
Abducens - eye movement (LR)
motor
What does CN VII do?
Facial- facial movement, taste from anterior 2/3 of tongue, lacrimation, salivation (submandibular and sublignual glands), eyelid closing (orbicularis oculi), stapedius muscle in ear (note: nerve courses through the parotid gland, but does not innervate it)
Both
What does CN VIII do?
Vestibulocochlear- hearing and balance
Sensory
What does CN IX do?
glossopharyngeal- taste and somatosensation from posterior 1/3 of tongue, swallowing, salivation (parotid gland), monitoring carotid body and sinus chemo- and baroreceptors, and stylopharyngeus (elevates pharynx, larynx)
Both
What does CN X do?
Vagus- taste from epiglottic region, swallowing, soft palate elevation, midline uvula, talking, coughing, thoracoabdominal viscera, monitoring aortic arch chemo- and baroreceptors
both
What does CN XI do?
Accessory- head turning, should shrugging (SCM, and trapezius)
Motor
What does CN XII do?
hypoglossal- tongue movement
Motor
Mnemonic for motor or sensory of CNs
Some Say Marry Money But My Brother Says Big Brains Matter Most
What CNs travel through the middle cranial fossa?
II-VI
What traverses the optic canal?
CN II, ophthalmic a., central retinal vein
What traverses the superior orbital fissure?
III, IV, V1, and VI
ophthalmic vein
sympathetic fibers
What traverses the foramen rotundum?
CN V2
What traverses the foramen ovale?
CN V3
What traverses the foramen spinosum?
middle meningeal a.
What CNs travel through the posterior cranial fossa?
CN VII-XII (through the temporal or occipital bone)
What traverses the internal auditory meatus?
CN VII, VIII
What traverses the jugular foramen?
CN IX, X, XI, and the jugular vein
What traverses the hypoglossal canal?
CN XII
What traverses the foramen magnum?
spinal roots of CN XI, brain stem, and vertebral aa.
Vagal nuclei pg 476
What mediates the corneal reflex?
Afferent: the nasociliary branch of the ophthalmic branch (V1) of the (trigeminal nerve sensing the stimulus on the cornea, lid, or conjunctiva (i.e., it is the afferent).
Efferent: VII (temporal branch: orbicularis oculi)
The corneal reflex, also known as the blink reflex, is an involuntary blinking of the eyelids elicited by stimulation of the cornea (such as by touching or by a foreign body), though could result from any peripheral stimulus. Stimulation should elicit both a direct and consensual response (response of the opposite eye). The reflex occurs at a rapid rate of 0.1 seconds. The purpose of this reflex is to protect the eyes from foreign bodies and bright lights (the latter known as the optical reflex). The blink reflex also occurs when sounds greater than 40-60 dB are made
What mediates the lacrimation reflex?
Afferent: V1 (loss of reflex does nor preclude emotional tears)
Efferent: VII
What mediates the jaw jerk reflex?
Afferent: V3 (sensory- muscle spindle from the masseter)
Efferent: V3 (motor- masseter)
The jaw jerk reflex or the masseter reflex is a stretch reflex used to test the status of a patient’s trigeminal nerve (CN V) and to help distinguish an upper cervical cord compression from lesions that are above the foramen magnum. The mandible—or lower jaw—is tapped at a downward angle just below the lips at the chin while the mouth is held slightly open. In response, the masseter muscles will jerk the mandible upwards. Normally this reflex is absent or very slight. However in individuals with upper motor neuron lesions the jaw jerk reflex can be quite pronounced.
What mediates the pupillary reflex?
Afferent: II
Efferent: III
What mediates the gag reflex?
Afferent: IX
Efferent: X
How would a CN V motor lesion present?
jaw deviates toward the side of lesion due to unopposed force from the opposite pterygoid muscle
How would a CN X lesion present?
uvula deviates away from the lesion side.
How would a CN XI lesion present?
weakness turning the head to the contralateral side from the lesion (SCM). Shoulder droop on side of lesion (trapezius)
NOTE: The SCMs help turn the head to the opposite side
How would a CN XII lesion (LMN) present?
tongue deviates toward the side of the lesion (‘lick your wounds’) due to weakened tongue muscles on the affected side
What is the cavernous sinus?
a collection of venous sinuses on either side of the pitutiary. Blood from he eye and superficial cortex drains to the cavernous sinus and then to the internal jugular vein
What things pass through the cavernous sinus?
CN III, IV, V1, and VI and occasionally V2 plus postganglionic sympathetic pupillary fibers all pass through en route to the orbit
the cavernous portion of the internal carotid a. also passes
What is Cavernous sinus syndrome?
presents with variable ophthalmoplegia, decreased corneal sensation, Horner syndrome and occasional decreased maxillary sensation
What can cause Cavernous sinus syndrome?
Secondary to a pituitary tumor mass effect, carotid-cavernous fistula, or cavernous sinus thrombosis related to infection
What CN is most susceptible in Cavernous sinus syndrome?
CN VI
Auditory physiology: Outer ear
the visible portion of the ear (pinna), includes the auditory canal and eardrum
transfers sound waves vai the vibration of the eardurm
Auditory physiology: Middle ear
Air filled space with three bones called the ossicles (malleus, incus, and stapes)
Ossicle conduct and amplify sound from the eardrum to the inner ear
Auditory physiology: Inner ear
Snail-shaped, fluid filled cochlea (below). Contains the basilar membrane that vibrates secondary to sound waves.
Vibration is transduced via specialized hair cells causing auditory nerve signaling to the brainstem
Each frequency of sound in the inner ear leads to vibration at a specific location on the basilar membrane (tonotopy). Where is low frequency heard?
at the apex near the helicotrema (wide and flexible)
Each frequency of sound in the inner ear leads to vibration at a specific location on the basilar membrane (tonotopy). Where is high frequency heard?
at base of cochlea (thin and rigid)
How would conductive hearing loss present?
abnormal rinne test
weber test localizing to the affected ear
How would sensorineural hearing loss present?
normal rinne test (air > bone)
weber test localizes to the unaffected ear
How would noise-induced hearing loss present?
damage to the stereociliated cells in the organ of Corti causes loss of high frequency hearing first
What is cholesteatoma?
overgrowth of desquamated keraton debris within the middle ear space that may erode the ossicles and/or mastoid air cells leading to conductive hearing loss
How would a UMN facial lesion present?
lesion of the motor cortex or connection between the cortex and facial nucleus causes contralateral paralysis of the lower face with the forehead being spared due to bilateral UMN innervation
How would a LMN facial lesion present?
ipsilateral paralysis of the upper and lower face
What causes facial nerve palsy?
complete destruction of the facial nucleus itself or its branchial efferent fibers (facial nerve proper)
How does facial nerve palsy present?
peripheral ipsilateral facial paralysis (absent forehead creases and drooping smile) with inability to close th eye on the involved side
can occur idiopathically (call Bell palsy); gradual recovery in most cases
What are some associations of Facial nerve palsy?
Lyme disease, herpes simplex and less commonly herpes zoster (Ramsay Hunt Syndrome)
sarcoidosis, tumors, diabetes
What is the tx for facial nerve palsy?
involves steroids
What muscles close the jaw?
Masseter, teMporalis, Medial pterygoid
What muscles open the jaw?
lateral pterygoid
“It takes more muscles to keep your mouth shut”
All muscles involved in jaw movement are innervated by what nerve?
V3 of the trigeminal
