Motor Neuron Disease Flashcards
def
cluster of degenerative diseases characterised by selective loss of neurons in motor cortex, cranial nerve nuclei, anterior horn cells
does MND affect upper or lower motor neurons
both
what distinguishes MND from MS and polyneuropathies
no sensory loss or sphincter disturbance
what distinguishes MND from myasthenia gravis
MND never affects eye movements
what are the four different types of MND
1 amyotrophic lateral sclerosis (ALS) (most common)
2 progressive bulbar palsy
3 progressive muscular atrophy
4 primary lateral sclerosis
what are the features of amyotrophic lateral sclerosis (ALS)
loss of motor neurons in motor cortex and anterior horn
weakness + UMN signs (babinski positive)
LMN wasting or fasciculations
what are the features of progressive bulbar palsy
only affects cranial nerves IX-XII
what are the features of progressive muscular atrophy
anterior horn lesion only therefore no UMN signs
affects distal muscle groups before proximal
what are the features of primary lateral sclerosis
loss of Betz cells in motor cortex
therefore mainly UMN signs + marked spastic leg weakness
aetiology
unknown (free radical damage implicated)
pathology
progressive motor neuron degeneration and death with gliosis replacing lost neurons
what is gliosis
change in glial cells in response to damage of the CNS
what are common types of glial cells
astrocytes
microglia
oligodendrocytes
associations
MND is associated with frontotemporal lobar dementia from proganulin mutations
epi
males>females
common in >60yrs
history
limb weakness speech disturbance (slurring or reduction in volume) swallowing disturbance (choking on food) behavioural changes (disinhibition)
examination
combined UMN + LMN signs which affect several regions asymmetrically
what LMN features
muscle wasting
fasciculations
increased tone
decreased/absent reflexes
what are UMN features
increased tone
brisk reflexes
babinski positive
what would be expected on sensory examination of MND
normal
investigations
investigations are aimed to confirm the diagnosis of MND by providing evidence of combined UMN + LMN loss
1 bloods -raised CK 2 MRI (brain/cord) -exclude structural causes 3 LP -exclude inflammatory causes 4 EMG
what are you looking for on an EMG
features of acute and chronic denervation with giant motor unit APs in >1 limb
what is bulbar palsy
diseases of the nuclei of CNs IX-XII in the medulla
what are signs of bulbar palsy
UMN lesion of the tongue + muscles of talking + swallowing
- fasciculating tongue
- nasal speech
- jaw jerk is normal/absent + gag reflex is decreased
