Approach to weakness Flashcards
(31 cards)
What are the features of UMN (brain, brainstem, spinal cord) lesions?
- atrophy
- fasiculation
- tone
- clone
- reflexes
- plantars
- atrophy: less marked
- fasiculation: none
- tone: increased
- clone: >3 beats
- reflexes: increased
- plantars: upgoing
What are the features of LMN (root, plexus, peripheral nerve) lesions?
- atrophy
- fasiculation
- tone
- clone
- reflexes
- plantars
- atrophy: present, may be severe
- fasiculation: may be present
- tone: decreased
- clone: <3 beats
- reflexes: decreased
- plantars: downgoing
What are the features of LMN (NMJ or muscle) lesions?
- atrophy
- fasiculation
- tone
- clone
- reflexes
- plantars
- atrophy: usually absent, but severe myopathy may lead to atrophy, hypotonia and diminished reflexes
- fasiculation: none
- tone: usually normal
- clone: <3 beats
- reflexes: usually normal
- plantars: downgoing
[UMN hemiparesis: Localised to right brain] How would it present?
UMN hemiparesis with ipsilateral cranial nerve palsy, for instance, left hemiparesis with left facial droop in a right sided stroke.
Note that this would be an UMN CN VII palsy, involving only the lower half of the face.
[UMN hemiparesis: Localised to right brainstem] How would brainstem lesions present?
- example 1: left pons lesion?
- example 2: left midbrain lesion?
UMN hemiparesis with contralateral cranial nerve palsy at the level of lesion.
For example, a left pons lesion can result in right sided weakness with left LMN facial droop, involving both the lower and upper half of the face (due to involvement of the seventh nerve nucleus, which is an LMN).
Similarly, a left midbrain lesion can result in a right sided weakness and left third nerve palsy.
What are hyperacute causes of weakness (onset in minutes)?
usually vascular e.g. cerebrovascular accident and haemorrhage
What are subacute causes of weakness (onset over hours to days)?
- Inflammatory (e.g. Guillain- Barre syndrome, multiple sclerosis)
- Infective (e.g. bacterial meningitis, cranial abscess)
What are chronic causes of weakness (onset over weeks to months or longer)?
- Neoplastic
- Infective e.g. tuberculoma
- Degenerative e.g. Parkinson’s disease and cervical myelopathy
- Metabolic (e.g. diabetic neuropathy)
What are episodic causes of weakness?
- Migraine(hemiplegic migraine)
- Epilepsy (Todd’s paralysis post seizure)
- Thyrotoxic periodic paralysis
- Hypokalaemic periodic paralysis
[UMN Paraplegia/ Quadriplegia]
- If sensation is abnormal, the lesion is almost always at the _________.
- _____________ also suggests a spinal cord lesion, and is decidedly less common in lesions of other parts of the neuraxis.
- Proceed to find the level of the lesion, and consider the aetiology.
spinal cord (the terms ‘myelitis’ and ‘myelopathy’ refer to spinal cord disease);
Bladder and bowel sphincter dysfunction
[UMN Paraplegia/ Quadriplegia] What does a brisk jaw jerk imply?
a brisk jaw jerk implies cranial nerve involvement, suggesting something more than just spinal cord disease (e.g. MS, neuromyelitis optica [NMO], motor neuron disease [MND]).
[UMN Paraplegia/ Quadriplegia] How does syringomyelia present?
- Pain and temperature loss in a shawl like distribution over the shoulders, with sparing of fine touch and proprioception.
- UMN weakness in the upper limbs exceeds that in the lower limbs.
- This is due to an expanding fluid filled cavity in the centre of the spinal cord, which affects spinal cord structures closer to the centre
[UMN Paraplegia/ Quadriplegia] How does subacute combined degeneration due to vitamin B12 deficiency present?
UMN paraparesis with isolated proprioception and vibration loss, spinothalamic tracts are spared. This is classically due to vitamin B12 deficiency.
[UMN Paraplegia/ Quadriplegia] How does anterior cord syndrome present?
UMN paraparesis with isolated loss of pain and temperature with sparing of dorsal columns
[UMN Paraplegia/ Quadriplegia] How does complete section spinal cord at C1/ C2 region present?
Quadriplegia + incontinence + sensory loss + loss of voluntary control of breathing (paralysis of diaphragm → require artificial ventilation):
[UMN Paraplegia/ Quadriplegia] How does complete section of spinal cord at the mid cervical region present?
Quadriplegia/tetraplegia (no voluntary control over any limbs; paralysis from the neck down) + sensory loss (if complete lesion).
[UMN Paraplegia/ Quadriplegia] How does complete section of spinal cord at the mid thoracic region present?
Paraplegia (paralysis from the waist down) and incontinence (loss of voluntary control of bladder and bowel function):
[UMN Para/Quadriplegia with Normal Sensation] What are the differentials?
Bilateral brain disease
- Parasagittal lesion (e.g. meningioma): Classically bilateral lower limb diplegia, as the parasagittal segment of the motor homunculus supplies the lower limbs.
- Multiple strokes in both cerebral hemispheres.
MND: The combination of UMN and LMN findings (wasting or fasciculation) is classic for MND, however some variants (primary lateral sclerosis) are purely UMN.
Hereditary spastic paraparesis.
Cervical spondylotic myelopathy: Rarely may present with only subtle sensory findings.
[UMN weakness: Bizarre distribution] What are your differentials?
- Multiple strokes affecting different territories in the brain.
- Multiple sclerosis (MS)
- Multiple sclerosis mimics: MS has a number of mimics, including NMO, lupus and others.
- Motor neuron disease (MND)
[UMN weakness: Bizarre distribution] How does multiple sclerosis present?
- Younger patient (often 18- 59 years old) with CNS lesions in multiple anatomic locations (dissemination in space), and at different times (dissemination in time).
- This demyelinating disease can affect any part of the CNS, causing subacute onset transverse myelitis (bilateral UMN below the spinal cord level), incoordination, optic neuritis (visual deficit with pain on extraocular eye movements and a relative afferent pupillary deficit), gaze palsies or various patterns of sensory impairment.
- There are no LM features.
[UMN weakness: Bizarre distribution] How does motor neuron disease present?
- MND (amyotrophic lateral sclerosis) affects both UMN in the cerebral cortex, as well as anterior horn cells.
- This results in a classic paradox of mixed LMN (prominent wasting, fasciculation) and UMN signs in the same myotome.
- The best place to look for fasciculation is the tongue at rest in the mouth.
- Sensory abnormalities are absent, unlike MS.
- Note that MND is a heterogenous group, some have the classic mix of UMN and LMN, less common variants are purely LMN or purely UMN.
- Nerve conduction studies (NCS) are normal, but electromyography (EMG shows a denervation pattern.
[UMN weakness: Bizarre distribution] What are the investigation findings of Multiple Sclerosis?
- Contrasted MRI of the brain and spine demonstrates white matter lesions disseminated in space (there some typical sites) and time (e.g. both old and new lesions present at the same time).
- Lumbar puncture may review oligoclonal bands in the cerebrospinal fluid, although this is less commonly done now (see MacDonald diagnostic criteria).
[LMN weakness, normal sensation] Given that weakness is proximal, what are your differentials?
Anterior horn cell
- MND Spinal muscle atrophy
- MND Progressive muscle atrophy
- Polio
Neuromuscular junction
- MG (Ocular VS Generalised Fatiguability)
- LEMS (A/w SCLC, Improves w/ use)
Muscle: Most myopathies
- Alcohol
- Statins
- Hyperthyroidism
- Hypothyroidism
- Cushing’s
- Polymyositis
- Dermatomyositis
[LMN weakness, normal sensation] Given that weakness is distal, what are your differentials?
Anterior horn cell (usually present with proximal weakness but also can be distal)
- MND Progressive Muscle Atrophy
- Polio
Peripheral nerve: Pure motor neuropathy
- MMN (multifocal motor neuropathy): usually in upper limbs
- AMAN (acute motor axonal neuropathy)
- Charcot marie tooth
Muscle: Distal myopathy
- Myotonic dystrophy
- Nonoka myopathy
