Neuro Lect 4
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Defined as a loss of muscle power.
What are some characteristics of myopathic disorders?
- weakness (more proximal than distal)
- no muscle wasting/depression of DTRs until advanced stages
- normal abdominal and plantar reflexes
- no sensory loss or sphincter disturbances
What does the abrupt onset of weakness suggest?
- vascular like stroke
- certain toxic/metabolic disturbances
What does subacute (days to weeks) onset of weakness suggest?
What does weakness that develops slowly over months to years suggest?
What does episodic progression of weakness symptoms indicate?
What does steady progression of weakness symptoms indicate?
- neoplastic disorder or...
- motor degenerative conditions
What does rapid fluctuation of weakness symptoms over short periods of time indicate?
When should distribution of weakness and/or neuropathy symptoms be determined? Why is this important?
- restriction of daily activities
- difficultly performing previously easy tasks
- reduced exercise tolerance
- important because distribution may help localize lesion
What are the physical exam findings that indicate muscle impairment? What is the muscle weakness involved?
- can't forcibly close eyes: upper facial muscles
- impaired pucker: lower facial muscles
- can't raise head while prone: neck extensors
- can't raise head while supine: neck flexors
- can't raise hand above head: proximal arm muscles
- can't walk with hyperextending knee: knee extensors
- can't walk with heels touching floor: shortened achilles tendon
- can't lift foot while walking: anterior leg compartment
- can't walks without waddling gait: hip muscles
- must use knees to get up from floor: hip muscles
- can't rise from chair without using arms: hip muscles
Name the lipid lowering agents that can can drug induced myopathies.
- fibric acid derivatives
Name the antivirals that can cause drug induced myopathies.
Name the antimicrotubular that can cause drug induced myopathies.
Name the drugs of abuse that can cause drug induced myopathies.
- demerol (meperidine)
Name the antibiotics that can cause drug induced myopathies.
Name the malarials that can cause drug induced myopathies.
Can glucocorticoids can myopathies?
Shrinking of muscles (weakness) due to either a lesion of the lower motor neurons or the muscle itself.
Visible irregular spontaneous flickering of muscle fibers that looks like worms under the skin.
How is muscle tone assessed?
- moving muscle groups through P/AROM
Increased muscle tone that varies, is worse at the extremes of the range of motion and usually presents with exaggerated reflexes (arms-increased in flexor muscles, legs-increased in extensor muscles).
- spasticity (hypertonia)
- Note: implies UMN lesion, loss of inhibition of muscle stretch reflexes
Stiffness or inflexibility that persists throughout the range of motion due to muscle contraction.
- rigidity (hypertonia)
- Note: implies extrapyramidal/basal ganglia dysfunction
Limb is floppy and allows excessive movement.
- flaccidity (hypotonia)
- Note: implies LMN lesion or myopathic disorder
Absence of strength and loss of voluntary movement in a muscle.
paralysis (plegia= 0/5 strength testing, paresis= 2-3/5 strength testing)
What are the most commonly tested reflexes, and what is the reflex grading system?
- biceps: C5
- brachioradialis: C6
- triceps: C7
- patellar: L4
- ankle jerk: S1
- 4+: very brisk, hyperactive, clonus, abnl
- 3+: brisker than average, may indicate disease
- 2+: average, nl
- 1+: somewhat diminished, low nl
- 0: no response
What do the asymmetric reflex principles suggest?
- lateralization: typically UMN lesion on the brisk side
- focal deficit: root/plexus/peripheral nerve lesion
- loss of distal DTR with preservation of proximal: polyneuropathies (diabetes)
Why are upper motor neuron injuries common?
- large amount of cortex occupied by motor areas
- motor pathways extend all the way from cerebral cortex to lower end of spinal cord
What is the initial period of "hypotonia" after upper motor neuron injury (corticospinal tract)?
Neuron that connects the spinal cord to the target muscle, is the origin of motor fibers that make up the CN and peripheral nerves.
lower motor neuron (second order)
Disturbance at any point of the PNS can disturb motor function. What are the different points on the PNS?
- anterior horn
- nerve root
- limb plexus
- perihperal nerve
- neuromuscular junction
What are the signs of UMN injury (loss of negative stimulus) on the LMNs?
- diffuse weakness
- positive Babinski
- no muscle atrophy until late
- Note: LMN fires indiscriminately with loss of UMN function
What are the signs of LMN injury?
- flaccidity (focal weakness)
- negative Babinski
- wasting of muscles
- hyporeflexia (diminished)
- Note: positive stimulus is gone, receives no messages from the UMN (brain)
What are the different gait abnormalities and what are the possible causes for each?
- can't stand without use of hands: deconditioning, myopathy, hip/knee pain
- unsteadiness upon standing: orthostatic HOTN, balance problems, generalized weakness
- stagger with eyes closed: vision compensating for defect
- short steps: weakness, parkinson's disease
- asymmetry: CVA, focal pain, arthritis
- wide based gait: fear, balance problems
- flexed knees: contractions, quad weakness
- slow gait: fear of falling, weakness, deconditioning, PVD, COPD, CHF, angina
What are the 7 classic gaits?
- hemiplegic: brain stem, cerebral hemisphere, stroke, tumor
- spastic diplegic: "scissor gait"
Gait with unilateral weakness and spasticity with the upper extremity held in flexion and the lower extremity in extension making it "too long". Patient will have to "circumduct" or swing the leg around to step forward.
hemiplegic gait (UMN lesion)
Gait in which the patient has spasticity in the lower extremities greater than the upper extremities. Hips and knees are flexed and adducted with the ankles extended and internally rotated. The patient circumducts the lower extremities while upper extremities are held in a mid or low guard position.
deplegic gait, "scissor gait" (periventricular lesions since the corticospinal tract axons that are going to the legs are closest to the ventricles)
Gait most often seen with peripheral nerve disease that mostly affects the distal lower extremity due to weak foot dorsiflexors (high stepping gait to avoid toe dragging). Caused by sensory neuropathy, vitamin B12, and tabes dorsalis.
neuropathic gait, aka steppage gait
Gait due to weak pelvic girdle muscles. Patient cannot stabilize the pelvis as they lift their leg to step forward so pelvis will tilt toward the non-weight bearing leg which results in a waddle type of gait.
Bradykinetic gait with small, shuffling steps. Also presents with pill-rolling hand tremor. Patient turns en bloc (like a statue) and has decreased facial expression. Gait described as "festinating".
Hyperkinetic gait seen with certain types of basal ganglia disorders. Presents with intrusion of irregular, jerky, involuntary movements in both upper and lower extremities giving a lurching appearance.
Wide based gait with truncal instability and irrgular lurching steps. Results in lateral veering and if severe, falling. Usually seen in midline cerebellar disease with a severe loss of proprioception.
One of the most common neurologic disorders in the USA (2nd most common cause of neurologic disability) that leads to a disease of inflammation and selective demyelination of the central nervous system. Northern European descent, and women (2x) more likely to get it. Onset is typically 20-45 yrs. Severity ranges from benign illness to profound disability.
What is the triad of symptoms caused by MS?
- gliosis formation
What are the characteristics of multiple sclerosis?
- focal demyelination: often periventricular
- classic CNS triad: inflammation, demyelination, gliosis formation
- scattered demyelination w/ reactive gliosis: affects brain white matter, spinal cord, optic nerve
What is the pathophysiology for multiple sclerosis?
- autoimmune process against myelin antigens
- T cells enter CNS and disrupt BBB but preserves the blood vessel wall
- demyelination causes slowed nerve conduction and neurologic symptoms
How does the onset of MS present and what is the diagnostic criteria?
- varied: virtually any neurologic symptom, severity depends on location, size of lesions and severity of lesion
- criteria: presence of CNS lesions separated by time and space
What are common symptoms at onset of multiple sclerosis?
- sensory loss
- optic neuritis
- bladder problems
- visual loss
- facial palsy
What are the common signs of multiple sclerosis?
- impaired vibratory sense
- optic neuritis
- intention tremor
What are the common visual abnormalities associated with MS?
- optic neuritis
- internuclear ophthalmoplegia (6th CN palsy)
Inflammation that causes unilateral vision loss over hours to days (max within 1 wk). Scotomata is noted on visual field testing, optic disk appears swollen and blurred, pupils are slow to react. Requires immunotherapy (steroids).
- optic neuritis (most common cause is MS)
- cormibid sxs include HA, orbital pain, eye pain with eye movement
Paresis of eye adduction in lateral horizontal gaze but not in convergence due to dysfunction of the medial longitudinal fasciculus (MLF) from a lesion in pons/midbrain. Is one of the most localizing brainstem syndromes.
- internuclear ophthalmoplegia/6th nerve palsy
- Note: MLF lesion blocks horizontal gaze signal to CN VI, convergence does not require input from here
Projects from the superior orbital fissure and innervates the lateral rectus muscle, is the primary adductor of the eyes.
CN VI- abducent nerve
6th nerve palsy is the most common isolated palsy seen in patients with what conditions?
- late syphillis
A lesion on CN VI results in alternating abducent hemiparesis and what other defects?
- convergent medial strabismus (esotropia) with inability to abduct the eye
- horizontal diplopia
What are the clinical manifestations of multiple sclerosis?
- limb weakness: lost strength, fatigue, gait disturbance
- typically exercise induced
- UMN type: spasticity (legs), Babinski sign, hyperreflexia
- sensory sxs: parasthesias/hypesthesias (dead sensations)
- ataxia: common with involvement of the cerebellum
- bladder and bowel dysfunction: common
- cognitive dysfunction: memory loss, problem solving difficulties
- depression: very common
- fatigue: 90% of MS pts, most common cause of work related disability
What is the prognosis for most patients with MS?
- progressive disability
- 20% will have NO limitations after 15 years
- 50% will require assistance with ambulation
- >80% will require assisted ambulation after 25 years
What factors make prognosis for pts with MS more favorable?
- sensory symptoms at onset
- complete recovery from episodes
- <40 years
- minimal impact after 5 years
- RRMS w/ <2 episodes in the first years
What is the hallmark of diagnoses for MS?
- two or more episodes of symptoms
- two or more signs
Involvement of anatomically noncontiguous white matter tracts of the CNS, symptoms last longer than 24hrs and distinct episodes are separated by a month or more are diagnosis criteria for what disease?
What test is the most useful to confirm diagnosis of MS? What findings in this test are required?
- evidence of at least two different regions of central white matter are affected at different times; bright lesions in the white matter of the cerebral hemispheres, brain stem and spinal cord (contrast enhances lesions)
- Note: bright lesions of MS may be indistinguishable from subcortical infarctions so clinical knowledge of the pt is crucial
What tests help diagnose multiple sclerosis?
- CSF protein electrophoresis (IgG bands)
- evoked potentials (electrical means of assessing function in afferent/efferent pathways)
Episodes of worsening symptoms with complete recovery between episodes, with the initial course of 85% to 90% of individuals with MS. Consists of unpredictable relapses followed by periods of remission with no new signs of disease.
relapse remitting (MS)
80% of those with initial relapsing-remitting MS who then begin to have neurologic decline between their acute attacks without any definite periods of remission. May include new neurologic symptoms, worsening cognitive function, or other deficits. The most common type of MS and causes the greatest amount of disability with failure to have complete recovery between episodes.
secondary progressive (MS)
Approximately 10% of individuals who NEVER HAVE REMISSION after their initial MS symptoms. Decline occurs continuously without clear attacks.
primary progressive (MS)
Progressively worsening MS symptoms with episodes of exacerbations without complete recovery. Represents a steady neurologic decline. Pt will have superimposed attacks.
progressive relapsing (MS)
What are the three categories of treatment for MS?
- tx acute attacks
- disease modifying agents that reduce biologic activity of MS
- symptomatic therapy
How are acute MS flare ups generally managed?
- glucocorticoids (methyprednisolone 500-1000mg/d for 3-5 days, then prednisone 60-80mg tapered over 2 weeks)
- hold tx for MILD flares
- increased ambient temp/fever/infection during pseudoexacerbations treated accordingly
What is the aim of disease modifying agents in treating MS? What is the long term goal?
- slow relapses, delay onset of significant disability
- longer term includes tx with beta-interferon (avonex 30mcg IM qweek, glatiramer acetate 20mg SQ qd)
What are the agents used to treat spasticity with MS?
How is MS treated without pharmacotherapy?
What are the spinal cord "red flag" symptoms?
- history of trauma
- recent unexplained weight loss
- pain worse at night (r/o malignancy)
- bowel or bladder incontinence (r/o cauda equina syndrome-needs urgent MRI)
Spinal cord disorder that is a true emergency, needs treatment within 6 hours, and is often associated with antecedent history of back/radicular pain (at level of lesion), UMN weakness, sensory loss and bladder dysfunction (below level of lesion).
How is spinal cord compression evaluated for? What area of the spine is most often affected? What test should you start with the neuro exam is normal?
- MRI and/or CT myelography (emergent referral no neurology with abnormal PE)
- thoracic spine
- spinal xray
What are intramedullary tumors that can be found as a cause for spinal cord compression?
- Note: most metastatic tumors are located in the extradural space
What are extra medullary and intramural tumors within the dura but now the spinal cord that can cause spinal cord compression?
- schwannoma (neurofibroma)
- Note: most metastatic tumors are located in the extradural space
How is spinal cord compression treated?
- IV corticosteroids
- surgical decompression
What are the features of spinal cord metastasis?
- sensory disturbance
- sphincter dysfunction
What is the etiology for spinal cord shock?
- acute cord injury
- form of distributive shock
What are the three primary findings in a pt with spinal cord shock? What injury is it most commonly associated with?
- paralyses with areflexia
- sensory loss
- autonomic paralysis
- most common associated with cervical level injury
What condition results in a loss of sympathetic tone, reduction in systematic vascular resistance, hypotension WITHOUT compensatory tachycardia (bradycardia, syncope)?
Clinical findings of what condition consist of hyperdynamic heart sounds, warm extremities, wide pulse pressure with large stroke volume and hyperdynamic left ventricle on EKG?
- spinal shock
- Note: fluids have minimal effect on BP, urinary o/p or mentation
How is a patient with spinal shock who is minimally responsive or unresponsive treated?
- one ampule 50% dextrose
- 2mg naloxone IV/IM
- A line and Foley catheter
- labs (CBC, chem 12, ABG, coags, type and cross and bacterial cx)
Cord transection above C3-C5 is likely to result in what?
Cord transection/lesion at T6 results in what?
lost abdominal reflexes
Cord transection/lesions above the sacral level can cause what?
bowel and bladder dysfunction
How can pts get Horner's syndrome from a cord transection?
secondary to disruption of sympathetic fibers through the upper cervical spinal cord
What level of cord lesion/transection leaves a patient dependent on others and requires respiratory support, is dependent on others for assistance with transfers, and requires an electric wheelchair for mobility?
C1-C4 (high quadraplegia)
What level of cord lesions/transection leaves a patient partially independent with adaptive equipment (self care), may be dependent or not dependent with transfers, and may use a manual wheelchair and drive with adaptive equipment?
C5-C8 (low quadriplegia)
What level of cord lesion/transection leaves a patient independent with self care and transfers, and allows them to ambulate short distances with assisted devices?
below T1 (paraplegia)
Condition from partial cord transection that causes diminished motor strength and fine touch, position and vibration sensation on the side of injury. Results in loss of pain and temperature sensation on the side opposite the injury.
- Brown-Sequard syndrome
- Note: segmental findings with spinal cord hemisection will depend on the level of the lesion and its rostro-caudal extent
Condition in which nucleus pulposus "herniates" and presses on nerve root that may come on with heavy lifting (or not). Pts get radicular symptoms along the nerve distribution.
intervertebral disc prolapse
Where is interveterbral disc prolapse most common? What are the symptoms?
- L4-L5, and L5-S1
- back pain, abnormal posture, limitation of spine motion, radicular pain (dermatome distribution, lost DTRs suggestive of root lesion)
How is acute intervertebral disc prolapse evaluated for?
- plain xrays (no neuro deficit)
- CT/MRI (with neuro defecit/persistent pain despite conservative tx)
What is conservative treatment for acute intervertebral disc prolapse?
- analgesia (NSAID/tylenol/muscle relaxor)
- PT (formal/informal)
- tincture of time
What is the surgical management of acute intervertebral disc prolapse?
- partial hemilaminectomy with excision of prolapsed disc
- fusion if spine is unstable
- Note: neurosurg eval on pts with radicular sxs or signs
What are the four indications for surgical treatment of an acute intervertebral disc prolapse?
- progressive motor weakness (nerve root injury)
- bowel/bladder disturbance or other signs of cord compression
- incapacitating pain for at least 4 weeks
- recurrent incapacitating pain despite conservative treatment
Centrally prolapsed disc causing bilateral sxs of "saddle" anesthesia, bladder/bowel dysfunction, wasting, weakness, fasciculation, and significant pain by affecting the spinal roots within the lumbar and sacral regions.
- cauda equina syndrome
- Note: DOES NOT AFFECT THE SPINAL CORD!
If the lesion causing cauda equina syndrome affects the conus medullaris as well what findings should be looked for?
- mix of upper motor nerve findings with sphincter dysfunction and radicular pain
- intact leg strength and reflexes if lesion is below the lumber cord
Lesion of the right dorsal column at L1 produces what impairment?
absence of light touch, vibration, position sensation in the RIGHT leg (only fasciculus gracilis exists below T6)
What are common causes for right dorsal column lesions, right fasciculus cuneatus lesions, right lateral corticospinal tract lesions, and right lateral spinothalamic tract lesions or hemicord lesions (brown-sequard syndrome)?
- penetrating injuries
- compression from tumors
Lesions of the right fasciculus cuneatus at C3 produces what impairment?
absence of light touch, vibration, position sensation in the RIGHT arm and upper trunk
Lesions of the right lateral corticospinal tract at L1 produces what impairment?
upper motor neuron signs (weakness/paralysis, hyperreflexia, hypertonia) in the RIGHT leg
Lesions of the right lateral spinothalamic tract at L1 produces what impairment?
absence of pain and temperature sensation of the LEFT leg
Lesions of the anterior gray and white commissures (central cord syndrome) at C5-C6 produces what impairment?
absence of pain and temperature sensation in the C5 and C6 dermatomes in BOTH upper extremities
What are common causes for lesions of the anterior gray and white commissures (central cord syndrome) at C5-C6?
- post traumatic contusion and syringomyelia
- intrinsic spinal cord tumors
Complete transection of the right half of the spinal cord (hemicord/Brown-Sequard syndrome) at L1 produces what impairments?
- absence of light touch, vibration, position sense in the RIGHT leg (dorsal columns @ L1)
- upper motor neuron signs in the RIGHT leg/monoplegia (corticospinal tract @ L1)
- absence of pain and temperature sensation in LEFT leg (spinothalamic tract @ L1)
Complete transection of the spinal cord (transverse cord lesion) at L1 would produce what impairments?
- dorsal columns (bilat): absent light touch, vibration, position sense in BOTH legs
- lateral corticospinal tracts (bilat): upper motor neuron signs in BOTH legs (paraplegia)
- lateral spinothalamic tracts (bilat): absent pain and temperature sensation in BOTH legs
What are common causes for transverse cord lesions?
- transverse myelitis
Complete transection of the dorsal columns (posterior cord syndrome) in the CERVICAL region would produce what impairments?
absent light touch, vibration, position sense BILATERALLY from neck down (below lesion)
Complete transection of the lateral corticospinal and lateral spinothalamic tracts with sparing of the dorsal columns bilaterally (anterior cord syndrome) in the CERVICAL region would produce what impairments?
- corticospinal tracts: upper motor neuron signs bilat below level of lesion (dmg to LMNs in ventral horns cause LMN signs bilat AT the level of the lesion)
- spinothalamic: absent pain and temperature sensation bilat below level of lesion
- spared dorsal columns: light touch, vibration, position sense are intact throughout
What are the common causes of posterior cord syndrome (transection of dorsal columns-fasciculus gracilis & cuneatus)?
- compression from posteriorly located tumor
What are the common causes of anterior cord syndrome (transection of lateral corticospinal & spinothalamic tract bilat)?
- anterior spinal artery infarct
Disease caused by destruction of the anterior horn of the spinal cord. Pts present with mixed upper and lower motor neuron deficits in the limbs, as well as difficulty swallowing, chewing coughing, breathing, speaking (bulbar involvement), and tongue fasciculations (CLASSIC). Intellect is normal.
amyotrophic lateral sclerosis (ALS)
What studies are used to determine the diagnosis of ALS? What are some of the findings?
- muscle biopsy: may reveal denervation atrophy
- nerve biopsy
- EMG: fasciculations & fibrillations in upper and lower limbs, normal motor conduction velocity, normal sensory conduction
What pharmacotherapy is used to treat ALS? How does it work?
- inhibits glutamate release and slows progression but only prolongs survival by several months
How are the symptoms of ALS managed?
- spasticity: baclofen 5mg po TID
- mobility: electric wheelchair
- dysphagia: eventual feeding via PEG tube
- excess salivation: amytriptyline (anticholinergic)
- dysarthria: communication devices
- respiratory failure: positive pressure ventilation
What is the prognosis for patients with ALS?
progressive disease fatal in about 3 years
Viral infection that causes destruction of anterior horn cells in the spinal cord. Usually transmitted via fecal-oral route. Symptoms include weakness of paralysis (minority) following a prodromal phase. Can affect the respiratory muscles ("iron lung").
How is poliomyelitis diagnosed? How is it treated?
- viral isolation from stool or NP secretions
- no specific treatment
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