9. Weakness Flashcards
What are general systemic causes of weakness?
Infectious
Neurologic
Toxic logic.
Metabolic
Physiologic
Key points in weakness history
Nature, onset, progression of symptoms, exacerbation, or alleviating factors, fluctuations, and severity
Ask about review of symptoms, including cardiovascular, pulmonary, metabolic, infection, toxic, ingestion, medication, imbalance, or malignancy
List five non-neurologic causes of weakness
Alterations and plasma volume, i.e. dehydration
Alterations, and plasma composition – glucose, electrolytes.
Derangement in circulating, red cell – anaemia or polycythemia
Decreasing cardiac function – MI.
Decrease in systemic vascular resistance – vasodilator shock.
Increased metabolic demand – local or systemic infection, endocrinopathy, toxin
Mitochondrial disfunction – severe sepsis or toxin mediated.
Global depression of the CNS – sedatives, stimulant withdrawal
Physical exam key points for weakness
Vital signs
Physical exam, head to toe, including skin and mucous membranes
Patient presents with generalized weakness with no focal loss of muscle power – where should you focus your assessment?
Non-neurologic weakness
Patient presents with unilateral weakness: combination of arm, hand, or leg? What do you need to ask? Ask yourself? And what is your differential?
ipsi face involvement? Region of the cerebral cortex, corona radiata, internal capsule.
Contralateral, face, involvement or other CNS deficits – lesion of the brain stem
No involvement: lesion of the medial cerebral cortex, discrete, CT lesion or Brown sequard hemi syndrome
You know lateral weakness: one limb only? If yes, what to consider next for assessment/differential.
Signs of radiculopathy, Plex apathy neuropathy? If yes, consider discreet motor lesion, brown sequard with contralateral pain, loss, neuromuscular junction, if no sensory deficit
No, consider diabetic with upper extremity weakness and no loss of power
If a patient has bilateral weakness, what things do you need to consider and what is your differential diagnosis?
- Lower extremities: Auntie record, equina, GBS
- versus upper extremity: central cord syndrome
- All four extremities: cervical anterior cord syndrome versus GBS
- Proximal extremities only: consider myositis, rhabdomyolysis, neuromuscular junction disorder.
- Distal extremities: consider lower extremities, GBS, chronic poly neuropathy versus.
Upper extremity only: central cord syndrome
If patients have facial muscle weakness, only, what do you you need to consider in your differential diagnosis and assessment?
Isolated cranial nerve seven: mastoiditis, parotitis, idiopathic
Vs
Not isolated to cranial nerve seven: consider a brain, stem lesion, a muscular junction disorder, or cranial polyneuropathy
What general focal findings on exam indicate that weakness is more likely a potential neurologic cause
Lateralizing weakness
Numbness
Gait and stability.
Cranial nerve defects
Moderate loss of power versus complete loss of motion, medical terms
Paresis
Plegia
What neurologic signs might localize the unilateral weakness problem to the cortex?
Associated neglect
Visual field loss.
Expressive receptive aphasia
A facial droop with forehead involvement is more likely what as a cause of issue?
Cranial nerve seven has forehead involvement
Stroke means that they will still have the ability to raise both eyebrows and show crinkling
Brown sequard: what is this?
Internal capsule or brainstem lesion if the patient has unilateral weakness, contralateral, body pain, and temperature disturbances below the level of motor weakness
What are signs of an upper motor neuron lesion is compared to a lower motor neuron
Upper typically later in disease has spasticity, Babinski reflex, hyperlexia
Name six causes of critical diagnosis for neuromuscular causes of weakness
- Ischemic or haemorrhagic stroke of the cerebral cortex or subcortical, or brain stem
- Spinal cord, ischaemia or compression – disc, abscess, hematoma.
- Peripheral nerve – GBS
- Neuromuscular junction: myasthenic or colonic crisis, botulism, tick paralysis, organophosphate poisoning.
- Muscle – rhabdo
Name six causes of emergent diagnosis of neuromuscular weakness
- Cerebral cortex or subcortical: tumor, abscess, demyleination
2 brainstem: demyelination - Spinal cord: transverse, myelitis or compression: disc, spondylolysis.
- Peripheral nerve: compressive apathy such as a haematoma or aneurysm, paraneoplastic vasculitis Uremia
- Muscle – inflammatory myositis.
Most peripheral lesions do/do not have some sensory component to their presentation?
They do, make sure you look at the dermatomes
When are neuromuscular junction disorders considered?
Proximal arm leg muscles, wrist, extensors, finger, extensors, or ankle Dorsey flexors with mild fluctuating weakness that is often worse in the day
What are the main causes of anterior cord syndrome?
External compression
Ischemia
Demyelination
Non-emergent causes of peripheral neuropathy
Connective tissue disorder
External compression: entrapment syndrome, compressive Plexopathy
Endocrinopathy like diabetes
Paraneoplastic syndrome
Toxins, including alcohol
Trauma
Vitamin deficiency
What is the classic concerning finding for GBS?
As symmetric weakness from lower extremities to upper, sensory findings, parallel the weakness and reflexes will likely be decreased at some point in the clinical course
Differential diagnosis for common, acute proximal muscle weakness causes
Inflammatory, like polymyositis or dermatomyositis
Necrosis – including Rhabdo from HMG-CoA 3 reductase inhibitors
Muscles are often tendered to palpation
Differential diagnosis for chronic or recurrent my fibre pathology
Muscular dystrophy
Channel apathies such as hyperkalaemic and hypokalaemic periodic paralysis.
Metabolic myopathy or mitochondrial myopathy
Do you think you have an isolated cranial nerve 7 palsy but want to be sure it’s not brain stem. What other things do you need to check?
No extremity involvement.
No other cranial nerves involved.
Normal cerebellar testing.
Normal visual fields
What findings might indicate a more likely posterior cerebral circulation or brain stem disorder?
Sarabel findings.
Visual field defect.
Sensory disturbance.
Extremity upper motor neuron signs
What are the most common presentations for neuromuscular junction pathology?
Disfunction of one or more ocular, facial or frenal muscles
Name three abnormalities of pre-synaptic release at the acetylcholine for neuromuscular junction disorders
Botulism
Eaton Lambert
Organic phosphate poisoning
Name three medication’s that may worsen weakness inpatients with neuromuscular junction disease?
Aminoglycosides
Quinolones
Beta blockers
What is the main difference between cauda equina syndrome and conus medullaris syndrome?
Very similar, except conus is typically more bilateral, sacral segment occasionally is preserved bulbocavernosus reflex
