Neuromuscular and Muscular Disease

Question 1

Peripheral nervous system (PNS) and neuromuscular system are used interchangeably.
Describe the PNS

Answer 1

PNS has two major components, a motor and a sensory component.

Motor component begins w cell body in the anterior horn of grey matter (anterior horn cell). It projects a motor route anteriorly.

Sensory component begins in either skin or joint (travels to the posterior part of the spinal cord). The cell body lies outside the spinal cord, it lies in the dorsal root ganglion

Question 2

Answer 2

Question 3

Using this image, describe the structure of a nerve

Answer 3

• epineurium is the connective tissue sheath around the whole nerve
• bundles of nerve fibres which are wrapped in a perineurium
• in between nerve fibres, you have endoneurium

Question 4

What happens at the Neuromuscular juncton (NMJ) when the AP reaches the end of the nerve?

Answer 4

At the neuromuscular junction when the AP reaches the end of the nerve and then Ach is released, acts on nictoinic Ach receptor

Question 5

What are dermatomes and myotomes?

Answer 5

Dermatome - area of skin which is supplied by a single nerve root
E.g. T10 nerve root supplies sensation to the umbilicus region. Know:
- level of the nipple ⇒ T5
- level of umbilicus ⇒ T10
- suprapubically ⇒ T12

Myotomes - muscles supplied by a single nerve root
- e.g. C5 nerve root supplies multiple muscles - rhomboids, deltoid, supraspinatous

Question 6

What is the difference between peripheral and dematomal nerve innervation?

Answer 6

Sensory innervation from the Median nerve supplies skin over the thenar eminence, the thumb, index finger, middle finger and half of the ring finger (shaded)
Dermatomal innervation of the hand is DIFFERENT:
Thumb supplied by C6 sensory fibres, whereas middle finger is by C7 nerve root.
The fibres of C6 and C7 both travel in the median nerve
So: median nerve supplies thumb, index, middle finger and half of third finger but it does that via fibres that travel in different nerve roots.

Question 7

What would happen if you had a lesion in your median nerve? What about a lesion in C7?

Answer 7

Sensory innervation from the Median nerve supplies skin over the thenar eminence, the thumb, index finger, middle finger and half of the ring finger (shaded)
Lesion in median nerve - lose sensation in my thumb, index, middle and half of my ring finger
Lesion in C7 - lose sensation in middle finger only.

Question 8

Compare UMN vs LMN
(IMPORTANT FLASHCARD) 🥵

Answer 8

Question 9

Label this and use it to explain what Carpal Tunnel Syndrome is

Answer 9

Compression of the median nerve at the level of the wrist
One function of the median nerve is Abduction of the thumb (thumb up to the ceiling)
Patients with carpal tunnel will have weakness of thumb abduction.

Impaired sensory features in the distribution of the nerve and weakness in the distribution of the nerve

Question 10

Which symptoms are highly suggestive, and which are inconsistent with carpal tunnel?

Answer 10

Question 11

What is ulnar neuropathy?

Answer 11

Question 12

What is radial neuropathy?

Answer 12

Sensory disturbance in the distribution of radial nerve
Weakness in the muscles supplied by the nerve
The radial nerve supplies forearm extensors so you get a wrist drop.

High radial neuropathy - at the level of the axilla - the branches to the triceps are given off at that level - so you might also have weakness of elbow extension.

The level of numbness is classically over the dorsal radial aspect of the hand because the area supplied by the radial nerve and snuffbox.

Question 13

What is peroneal neuropathy?

Answer 13

Compression of the peroneal nerve in the legs
It supplies sensation over the dorsum of the foot and the lateral aspect of the calf.

You will get weakness of ankle dorsiflexion + ankle eversion

Question 14

What are polyneuropathies?

Answer 14

“Glove and stocking” distribution of weakness.
Most polyneuropathies are length dependent= start w longest nerve of the body. Pathology starts distally and then ascends to proximal nerves parts as the disease progresses.

The distance between sc and fingertip is shorter than the distance between lumbosacral spinal cord and toe - so toes are symptomatic first as its longest nerve
Symptoms start in the feet –>knee –>hands
Late stage - involvement of the shortest nerves - the intercostal nerves (sensation in the middle of the thorax becomes affected).

Question 15

What are the negative (aka hypofunction) signs of peripheral nerve disease?

Answer 15

Question 16

What are the negative (aka hypERfunction) signs of peripheral nerve disease?

Answer 16

Question 17

What are the causes of peripheral neuropathy?

Answer 17

Many causes of peripheral neuropathy. FAV EXAM QUESTION. know in particular:
- diabetes
- alcohol excess (alcohol is toxic to peripheral nerves)
- B12 deficiency
- uraemia
Porphyria (defect in production of heme) and lead poisoning are motor predominant neuropathies

Question 18

What is an inherited neuropathy?

Answer 18

Charcot-Marie-Tooth disease - aka hereditary motor and sensory neuropathy - group of inherited conditions that damage the peripheral nerves.
Muscles are thin
Cause LMN lesion
Joint deformities because of imbalance of muscle dynamics on the joints
Image shows clawed hammer toes. High arch of feet= pes cavus

Question 19

Peripheral neuropathy screen?

Answer 19

Question 20

What are the clinical manifestations of Guillain-Barre Syndrome?

Answer 20

Glove and stocking distribution of weakness
Involves peripheral nerves AND of nerve roots higher up (due to inflammation) - due to this, the nerve roots not only go to supply distal hands and ankles, but they also supply the proximal muscles.

The most common variant of Guillain-Barre Syndrome is AIDP
A - Acute - within four weeks
I - Inflammatory
D - Demyelinating - pathophysiology underlying it
P - Poly - polyradiculoneuropathy - multiple nerve roots and multiple nerves
= significant proximal + distal weakness.

Question 21

Multiple Mononeuropathy
(Mononeuritis Multiplex)= multiple nerves but not in a glove and stocking distribution. What are the causes of this?

Answer 21

Question 22

What are anterior horn cell disorders?

Answer 22

The anterior horn cell is the start of the LMN and it sits in the anterior horn of grey matter
Most common anterior horn cell disorder is MOTOR NEURONE DISEASE, of which there are different subtypes, eg ALS, PLS and flail limb

Question 23

Describe the 3 common types of motor neurone disease

Answer 23

Amyotrophic Lateral Sclerosis (ALS): UMN + LMN degeneration

Progressive muscular atrophy (PMA)/flail limbs: mainly LMN degeneration. does NOT have bulbar onset

Primary Lateral Sclerosis (PLS) : UMN degeneration

Question 24

Describe the bulbar, cervical and lumbar signs seen in motor neurone disease

Answer 24

Question 25

Why can you get tongue fasiculations?

Answer 25

Wasting and atrophy of the tongue due to degeneration of the anterior horn cells that go on to suppply the motor to the tongue via the hypoglossal nerve –> Tongue fasciculate

Question 26

What is radiculopathy and its causes?

Answer 26

Radiculopathy - problem with the nerve roots= painful
Common cause - structural compromise due to a prolapsed intervertebral disc.
Non-structural cause would be Guillian-Barre syndrome.

Question 27

Myasthenia Gravis is an NMJ disorder. Describe it

Answer 27

Autoimmune: Abs target the Ach receptor in the muscle membrane
Shouldn’t get any sensory disturbance in a neuromuscular junction disorder.
Clinical features: frequently affects the eyelids (ocular muscles), bulbar muscles (for speech, swallowing), proximal muscles of the limbs.
Fatigability - muscles get progressively weaker w ongoing use.

Question 28

Give another rare NMJ disorder

Answer 28

Another NMJ disorder called Lambert-Eaton myasthenic syndrome (LEMS) is a very rare condition that affects the signals sent from the nerves to the muscles.
It means the muscles are unable to tighten (contract) properly, resulting in muscle weakness and a range of other symptoms

Question 29

What is myopathy and what kind of weakness does it cause?

Answer 29

Myopathy is a problem with the muscles
You get proximal weakness with myopathy
No sensory disturbances - but you get limb girdle weakness (shoulders and hips)

Question 30

Give the causes of myopathy

Answer 30

Cushings syndrome: endogenous steroid production causes myopathy
Genetic causes - eg in Duchenne and Becker Muscular
Dystrophy there is a problem with distrophin gene (pseudohypertrophy of calf muscles). Oculopharyngeal muscular dystrophy also comes later in life
Facioscapulohumeral muscular dystrophy (FSHD= muscle weakness and atrophy; scapular winging as a result

Question 31

What are the adult inflammatory myopathies?

Answer 31

Question 32

What can patients with dermatomyositis present w?

Answer 32

proximal weakness, subacute, quite quick presentation

Question 33

How can you tell the difference clinically between axonal neuropathy and demyelinating neuropathy?

Answer 33

To tell the difference clinically between axonal neuropathy like diabetic neuropathy and demyelinating neuropathy like Guillian Barre syndrome - you have to do nerve conduction studies, which also tells us the severity, if its symmetrical etc. If aysemmetric more likley to be multiple neuropathy

1 In these studies you measure: how big the nerve response is (axonal neuropathy - lost axons - reduction of nerve amplitude)

2 How quick the conduction is (conduction velocity). loss of myelin sheath - slowed conduction velocity