Diagnosing Weakness

Question 1

What are the 2 functions of the upper motor neurone?

What happens if the UMN dies?

Answer 1

1. start the message
2. stop the message

if the UMN dies, the muscle does not know how to stop, as the message continues

this results in increased tone - spasticity

Question 2

What are the different levels of weakness?

Answer 2

• neurologically unexplained
• upper motor neurone
• lower motor neurone
• neuromuscular junction
• muscle fibre

Question 3

What part of the brain / spinal cord is damaged if there is weakness on one half of the body / all four limbs / both legs / one limb?

Answer 3

• one half of the body - cerebral hemisphere
• all four limbs - high cervical spinal cord
• both legs - low cervical spinal cord
• one limb - spinal root or peripheral nerve

Question 4

What pattern of weakness is present in generalised distal weakness and generalised proximal weakness?

Answer 4

• generalised distal weakness - peripheral neuropathy
• generalised proximal weakness - myopathy myasthenia

Question 5

What is meant by monoplegia, hemiplegia, diplegia and quadriplegia?

Answer 5

monoplegia:

• affects one limb only - usually an arm

hemiplegia:

• affects one side of the body including arm, leg and trunk

diplegia:

• affects symmetrical parts of the body (arms or legs)

quadriplegia:

• affects all four limbs

Question 6

What are the 4 stages involved in investigating weakness?

Answer 6

1 - history:

• explore the symptoms
• what? where? how long?

2 - examination:

• clinical findings
• muscle volume, strenght, tone, reflexes, involuntary movements

3 - tests:

• genetics, pathology (biopsy and imaging)
• looking for gene defects or abnormal muscle structure

4 - function:

• EMG and NCS

Question 7

What are the causes and clinical findings of an upper motor neurone problem?

Answer 7

causes:

• stroke
• infection
• tumour
• degeneration

clinical findings:

• brisk reflexes
• pathological reflexes
• mild atrophy
• stiffness

Question 8

WHat are the causes and clinical findings of a lower motor neurone disorder?

Answer 8

causes:

• infection
• toxin
• radiation
• degeneration
• trauma

clinical findings / localisation:

• anterior horn
• radiculopathy
• two or more nerves
• generalised peripheral neuropathy
• single nerve injury

Question 9

What are the signs of a LMN axonal lesion?

Answer 9

• weakness +/- numbness
• reduced relflexes
• muscle wasting
• fasciculation

Question 10

What are the 2 main conditions affecting the neuromuscular junction?

Answer 10

• myasthenia
• myasthenic syndrome

Question 11

What are the symptoms and signs of a problem at the neuromuscular junction?

Answer 11

• proximal weakness
• fatigability
• worse as the day goes by
• normal sensation
• normal reflexes
• repetitive nerve stimulation (RNS)

Question 12

What are the 2 main disorders resulting from problems with muscle fibres?

Answer 12

• myopathy
• myositis

Question 13

What are the symptoms and signs of muscle disease?

Answer 13

• progressive weakness - usually proximal
• normal sensation
• normal reflexes
• normal tone
• moderate wasting
• can be congenital, inherited, metabolic, toxic or mitochondrial

Question 14

What is motor neurone disease?

What causes it?

Answer 14

a disease of motor neurones which is progressive

• can be idiopathic (unknown cause)
• 5-10% cases have a genetic cause (familial basis)
• can be caused by toxins, viruses, trauma or combinations
• tends to be sporadic (here and there)

Question 15

Where do UMN and LMNs originate?

Answer 15

UMN originate in frontal motor gyrus - brainstem and spinal cord

LMNs have their cell bodies in the spinal cord

Question 16

What happens in ALS?

Answer 16

Cells in the CNS and PNS start dying and there is cellular apoptosis

the lysosomes then digest the cells

Question 17

What are the symptoms and signs of motor neurone disease?

Answer 17

• painless
• no loss of feeling
• progressive bulbar palsy - weakness in the tongue, the face and the palate
• dyphasia
• dysarthria
• nasal regurgitation and aspiration

Question 18

What is life expectancy with MND?

Which functions are preserved in this condition?

Answer 18

life expectancy is 3-5 years - it is progressive with no remission

• normal cognition
• eye muscles are preserved
• sphincter function is preserved
• sexual activity is preserved

Question 19

What are the different clinical forms of MND?

Answer 19

• progressive muscular atrophy (PMA)
• primary lateral sclerosis (PLS)
• progressive bulbar palsy (PBP)
• MND - FTD

Question 20

How are EMG and NCS performed?

Answer 20

UMN - LMN - muscle

Question 21

What is invovled in generating a nerve impulse and it travelling to form a spinal nerve?

Answer 21

• impulse generated in the cortex and passed to the anterior horn cell via CST or CBT
• LMN exits the spinal cord forming ventral rootlets
• the body of the sensory neurone lies in the dorsal ganglion
• dorsal ganglion has a peripheral arm and the axon, which travels all the way to the brainstem
• the dorsal and ventral roots come together to form spinal nerves

Question 22

What features of the motor system can be measured?

Answer 22

• amplitude
• duration
• latency
• conduction velocity
• F-wave