Weakness

Question 1

what is the upper motor neuron pathway

Answer 1

cortex > subcortical tracts > internal capsule > brainstem (decussation in pyramids) > spinal cord > anterior horns

Question 2

what is the lower motor neuron pathway

Answer 2

follows directly on from upper mn
ventral roots > plexi > peripheral nerves > neuromuscular junction > muscle

Question 3

what is pyramidal weakness

Answer 3

in upper motor neuron lesions unless paralysis is complete (plegia) a specific pattern is seen
in upper limbs, extensors are weaker than flexors
in lower limbs, flexors are weaker than extensors

Question 4

what does the suffix paresis mean

Answer 4

mild-moderate weakness

Question 5

what does the suffix plegia mean

Answer 5

more severe weakness

Question 6

how are weakness patterns catergorised

Answer 6

according to the limb affected
mono - single limb (arm or leg)n
para - both legs
tetra - all four limbs (quadra is also used)
hemi - affecting arm and leg on one side

Question 7

what is the cortex

Answer 7

descending motor pathways begins here in the primary motor cortex
organised by body regions
large areas devoted to tongue, face and hand
lower limb is given a relatively smaller region on medial surface
lesions will selectively affect certain regions

Question 8

difference between cortical and diffuse lesiosns

Answer 8

cortical lesions only affect a selected region
diffuse lesions (major infarction) will affect a large area

Question 9

how do lesions in other upper motor neurons affect the body

Answer 9

lesions outwith the cortex affect broader territory
this is due to tracts travelling closely together

Question 10

what other clues are there to cortical lesions

Answer 10

seizures
other cortical deficits such as aphasia

Question 11

how do lesions in the corona radiata and capsule affect the body

Answer 11

lesions here affect broad anatomical territory (eg hemiparesis)

Question 12

what is the key to localisation of brainstem lesions

Answer 12

corticospinal tract decussates at the pyramids in the medulla
cranial nerves emerging from the brainstem tend to travel on the same side they emerge from
this leads to crossed signs - ipsilateral cranial nerve lesion contralateral signs in limbs
often lesions are very focal

Question 13

describe a cervical cord lesions

Answer 13

lesions affecting bilateral cord will produce tetraparesis/plegia
spasticity and brisk reflexes will be present, with upgoing plantars (Babinski reflex)
other markers may be sensory loss and a disturbance to bowel and bladder

Question 14

describe thoracic cord lesions

Answer 14

will only produce weakness in lower limbs
spastic tone, pyramidal weakness, brisk reflexes upgoing plantars
sensory disturbance
sphincter disturbance

Question 15

what is different about the cauda equina compared to the rest of the spinal cord

Answer 15

nerve roots descend before exiting via the foramina
these roots also carry autonomic and sensory fibres

Question 16

what can lesions in the cauda equina cause

Answer 16

bilateral paralysis
sensory loss
LMN signs (eg areflexia)
loss of bladder/bowel function
cauda equina syndrome is an emergency, threat of permanent paralysis

Question 17

what is radiculopathy

Answer 17

compression of nerves where they exit the spinal canal

Question 18

what are the causes of radiculopathy

Answer 18

prolapsed intervertebral disc
facet joint hypertrophy
spondylolisthesis
radiculitis (inflammation)

Question 19

symptoms of radiculopathy

Answer 19

pain which radiates down the nerve (radicular pain) dermatomal sensory loss with or without weakness in the site (LMN signs on exam)
examination may elicit characteristic pain via provocative manoeuvres, loss of reflexes in affected territory

Question 20

what are plexi and how does a lesion impact them

Answer 20

plexi are where spinal nerves combine and individual nerves emerge
lesions here produce a pattern of weakness not conforming to an individual root territory, nor peripheral nerve

Question 21

impact of peripheral nerve lesions

Answer 21

lesions here affect individual nerves (mononeuropathy)
signs will reflect loss of function in the region supplied by the specific nerve
usually sensory, can be with or without motor features
some nerves are sensory or motor only

Question 22

how do peripheral nerve lesions occur

Answer 22

nerves are damaged
can be due to a variety of processes such as compression, tumours or inflammation

Question 23

describe polyneuropathy

Answer 23

multiple nerves affected in multiple limbs (+/- cranial nerves)
various patterns exist but in general longest nerves are damaged first (‘glove and stocking’ sensory loss, distal weakness)
reflexes are diminished or absent
chronically will see wasting, sometimes fasciculations

Question 24

what is the neuromuscular junction

Answer 24

synapse between motor neuron and muscle

Question 25

what does issues with the NMJ appear as

Answer 25

fatigable weakness (sustained exertion on bedside testing causes decreasing power)
usual pattern is weakness affecting proximal muscles, ocular muscles, bulbar muscles, neck muscles
sensation is normal and reflexes are unaffected

Question 26

what is myasthenia gravis

Answer 26

autoimmune disorder where there are antibodies to acetylcholine receptor on muscle

Question 27

what is the treatment for myasthenia gravis

Answer 27

pyridostigmine (acetylcholinesterase)
immunosuoression
supportive measures
in some cases surgery
avoid drugs which may worsen the disorder

Question 28

what is muscle myopathy

Answer 28

when many different diseases exist affecting muscles
many different patterns exist
general pattern of proximal weakness, fatigability is not seen, reflexes are generally preserved, sensation is normal
other features include characteristic regions of atrophy (or hypertrophy), contractures, pain, dysmorphic features

Question 29

what is polymyositis

Answer 29

autoimmune disorder causing muscle inflammation
may be associated with underlying cancer

Question 30

what is the treatment for polymyositis

Answer 30

immunosuppression
supportive measures
screen for underlying cancer and treat if present