Muscle and Nerve Diseases Flashcards
Examples of muscles and nerve diseases; disorders of….
Muscle
NMJ
Peripheral nerve
Anterior horn cell
What does NMJ stand for?
Neuromuscular junction
Definition of a muscle
An intricate machine designed to convert chemical energy to mechanical energy
Presentation of muscle disease
Poor suck / feeding / failure to thrive / floppy Weakness of skeletal muscle SOB (resp muscles) Poor swallow (aspiration) Cardiomyopathy Cramp, pain, myoglobulinuria Wasting / hypertrophy of muscle Normal or reduced tone or reflexes Motor weakness
Definition of myoglobulinuria
Peeing black urine after exercise
Do you get sensory weakness in muscle disease?
NO
Classification of muscle diseases
Muscle dystrophies Channelopathies Metabolic muscle disease Inflammatory muscle disease Congential myopathies Iatrogenic - medication
How do most people get muscular dystrophies?
Genetic
What pattern of symptoms do you get with channelopathies?
Episodic symptoms
- completely fine, then an episodes and then back to completely fine
Types of muscular dystrophies
Duchenne's MD Becker's MD Facioscapulohumeral MD Myotonic dystrophy Limb Girdle MD
What happens in both duchennes and beckers MD?
Hypertrophy of the muscles
Infiltration of fat
Trouble of standing to sitting
Presentation of facioscapulohumeral MD
Facial weakness
Biceps
One other upper limb and lower limb proximal weakness
What can go wrong to cause muscle channelopathies?
Disorders of channels
- Ca
- Na
- Cl
What is the most common muscle channelopathy?
Familial hypokalaemia periodic paralysis
Types of muscle channelopathies
Familial hypokalaemia periodic paralysis
Hyperkalaemic periodic paralysis
Paramyotonia congenita
Myotonia congenita
In muscle channelopathies when they are having an episode and are weak, what is the key thing to measure? Why?
Potassium
Shows organic disease
Presentation of myotonia congenita
Bit of weakness
Muscles cannot relax after contract muscle - therefore feel very stiff
Types of metabolic muscle disease
Disorders of carbohydrate metabolism Disorders of lipid metabolism Mitochondrial myopathies/cytopathies Endocrinopathy Biochemical abnormalities
How does disorders of carbohydrate metabolism present?
Low level weakness with much more marked weakness on exercise
Give an example of an endocrinopathy condition that can give you muscle problems and how it does so
Cushings
- adrenal (production of steriods) causing the weakness - a steriod induced myopathy
What biochemical abnormality can give you muscle weakness?
Low potassium
What molecule is used for immediate rapid muscle activity e.g. sprinting?
Glucose
What is used up when muscles are used?
Energy
Examples of inflammatory muscle diseases
Polymyositis
Dermatomyositis
What does polymyositis affect?
ONLY muscles
What does dermatomyositis affect?
Skin
Muscles
What type of disorder, apart from inflammatory, is dermatomyositis?
Paraneoplastic
Presentation of inflammatory muscle disease
Painful weak muscles
Muscles sore to touch
If DM - characteristic rash
Feeling generally unwell
What age can get inflammatory muscle disease?
Any age
What is the characteristic rash of dermatomyositis?
Rash around eyes and knuckles
If a patient presents with painful weak muscles and a rash around eyes/knuckles, what should be done?
Look for an underlying tumour
Investigations of inflammatory muscle disease
Increased CK
EMG
Muscle biopsy
What would be find on biopsy in polymyositis?
CD8 cells
What would be found on biopsy in dermatomyositis?
Humeral mediated, B cells and CD4 cells
Treatment of inflammatory muscle diseases
Steriods
If dont work then a steriod suppressing immunosuppressant
When is CK in the blood elevated?
When there is a muscle disorder
Investigation of muscle diseases
History and exam CK EMG Muscle biopsy Genetic testing
What does the muscle biopsy look for?
Structure
Biochemistry
Inflammation
Give an example of a disorder of the NMJ
Myastenia gravis
Presentation of myastenia gravis
Fatiguable weakness
- eyelids (ptosis)
- proximal muscle weakness (face, neck, limbs)
- muscles of mastication (chewing, swallowing)
- talking
- SOB
- Diplopia
- dysphagia
Investigation of myastenia gravis
Single fibre electromyography
AChR ab (85 - 90%)
Anti MuSK ab (40%)
Neurophysiology (repetitive stimulation, jitter)
CT chest (thymoma)
Tensilon test; IV edrophonium reduces muscle weakness temporarily (not commonly used anymore due to risk of cardiac arrhythmia)
Treatment of myastenia gravis
Symptomatic - long acting acetylcholinesterase inhibitor e.g. pyridostigmine
Prednisolone or a steriod saving agent (to immunosuppress originally)
Thymectomy
Example of a steriod saving immunosuppresant
Azathioprine
How does an Ach Inhibitor give symptomatic relief in myastenia gravis?
Blocks the breakdown of Ach do have more of it at your endplate
How does immunoglobulin / plasma exchange work in myastenia gravis?
Immunoglobulin binds to the antibody and stops it binding to the NMJ
What does fatiguable weakness mean?
As you use the muscle, it is strong then gets weaker
Therefore muscles are fine in the morning but develop weakness later on in the day
Pathology of myastenia gravis
Anti AChR antibody blocks AchR so there is no muscle contraction
Flooded with ACh to outcompete this antibody but as the muscle fatigues it cannot do this as well
Where is the anterior horn cell found?
Between the UMN and LMN
What type of neurones are present in the LMN / PNS?
Both motor and sensory
What does peripheral nerve disease consist of?
Sensory axons
Autonomic nervous system
Types of sensory axons
Small fibres
Large fibres
What do small sensory fibres carry?
Pain
Temperature
What do large sensory fibres carry?
Joint position sense and vibration
Example of root disease
Degenerative spine disease
Examples of a lesion of an individual peripheral nerve
Compressive/entrapment neuropathy (entrapment e.g. carpal tunnel syndrome)
Vasculitis (mononeuritis multiplex) - if multiple nerves affected due to if blood vessels become inflamed/enlarged
Where does generalised peripheral neuropathy tend to present first?
Feet THEN hands
Presentation of generalised peripheal neuropathy
Motor
Sensory
Both
+/- autonomic features
Causes of generalized peripheral neuropathy
Metabolic - DM - alcohol - renal - B12 Toxic - drugs Hereditary Infectious - Lymes - HIV - leprosy Malignancy Inflammatory demyelinating - Acute - GBS - chronic - chronic inflammatory demyelinating polynueropathy
What does GBS stand for?
Guillian Barre syndrome
Presentation of a nerve root disorder
Myotomal wasting and weakness
Reflex change
Dermatomal sensory change
Presentation of disorder of an individual nerve
Wasting and weakness of innervated muscle
Specific sensory change
Presentation of generalised peripheral neuropathy
Sensory and motor symptoms starting distally and moving proximally
Investigations of peripheral neuropathy
Blood tests - vit B 12 deficiency - LFTs Genetic analysis (only if clear FH) Nerve conduction studies LP Nerve biopsy
Why do we tend to avoid nerve biopsies?
As could leave someone with a deficit
Presentation of MND
Combination of UMN and LMN signs
- UMN = increased tone, brisk reflexes, spasticity
- LMN = muscle fasiculations, wasting, weakness
No sensory involvement
Is there sensory involvement in MND?
No
Prognosis of MND
Die 2 - 5 years from symptom onset
Die 2 - 3 years from diagnosis
What % of patients die within 14 months of their diagnosis?
50%
What is usually the cause of death in MND?
Respiratory failure
Investigations of MND
Presentation - the unique combination of UMN and LMN signs
EMG
Treatment of MND
Supportive - PEG - NIV - Physio / OT / care Riluzole
How does riluzole work?
Anti glutamate antagonist - blocks the action of glutamate
Usually used in amyotrophic lateral sclerosis
Effects of riluzole on MND
Prolongs survival by a few months
N.B. some trials say it does nothing
Types of MND
Amyotrophic lateral sclerosis (50%)
Primary lateral sclerosis
Progressive muscle atrophy
Progressive bulbar palsy
Clues that would point towards a diagnosis of MND
Fasciculations
Absence of sensory symptoms
Mixture of UMN and LMN signs
Wasting of small hand muscles / tibialis anterior is common
Other common features of MND
Does NOT affect the external ocular muscles
NO cerebellar signs
Abdominal reflexes are usually preserved and sphincter dysfunction if present is a late feature
Features of amyotrophic lateral sclerosis
Typically LMN signs in the arms and UMN signs in the legs
What is the genetic abnormality in inherited amyotrophic lateral sclerosis?
Superoxide dismutase - on chromosome 21
Features of primary lateral sclerosis
UMN signs only
Features of progressive muscle atrophy
LMN signs only
Affects distal muscles before proximal
What type of MND carries the best prognosis?
Progressive muscle atrophy
Features of progressive bulbar palsy
Palsy of tongue, muscles of chewing/swallowing and facial muscles due to loss of function of brainstem motor nuclei
What MND type carries the worst prognosis?
Progressive bulbar palsy
Age of onset Beckers vs Duchennes
Duchennes - onset < 5 y/o
Beckers - onset > 10 y/o
Which of beckers and duchennes has LD?
Duchennes
Which of beckers and duchennes are associated with dilated cardiomyopathy?
Duchennes
Treatment for restless leg syndrome
Ropinirole
CK level in myasthesia gravis
Normal
Management of myasthenic crisis
Plasmapheresis
IV immunoglobulins
When does myotonic dystrophy occur?
20 - 30 y/o
What types of muscle does myotonic dystrophy affect?
Skeletal
Cardiac
Smooth
Two main types of myotonic dystrophy
DM1
DM2
Inheritance of myotonic dystrophy
Autosomal Dominant
Genetics of each type of Myotonic dystrophy
DM1 - CTG repeat at the end of DMPK gene on chromosome 19
DM2 - repeat expansion of the ZNF9 gene on chromosome 3
Main differences between DM1 and DM2
DM1 - distal weakness more prominent
DM2 - proximal weakness more prominent, and severe congenital form NOT seen
Presentation of myotonic dystrophy
Myotonic facies (long "'haggard" appearance) Frontal balding Bilateral ptosis Cataracts Dysarthria Myotonia Weakness of limbs - distal initially Mild mental impairment DM Testicular atrophy Cardiac involvement - heart block, cardiomyopathy Dysphagia
What is Eaton-Lambert syndrome associated with?
Small cell lung cancer
Ovarian cancer
Breast cancer
May also occur independently as an autoimmune disorder
Pathology of Eaton Lambert syndrome
Antibody directed against presynaptic voltage gated calcium channel in the PNS
Presentation of Eaton Lambert syndrome
Repeated muscle contractions lead to an increase in muscle strength (only seen in 50%) Limb girdle weakness (affects LLs first) Hyporeflexia Autonomic symptoms - dry mouth - impotence - difficulty micturating
Investigations of Eaton Lambert syndrome
EMG
- incremental response to electrical stimulation
Treatment of Eaton Lambert syndrome
Treatment of underlying cancer
Immunosuppression (e.g. with pred or azathioprine)
IV immunoglobulins and plasma exchange
MRC power scores
0 - no muscle movement
1 - trace of contraction
2 - movement at the joint with gravity eliminated
3 - Movement against gravity, but not against added resistance
4 - movement against external resistance with reduced strength
5 - Normal strength
What MRC power score indicates that the muscle can only work with gravity removed?
2
Involvement of T1 in erbs palsy may result in what?
Horners syndrome
Damage to the ulnar nerve results in what?
Wasting of hypothenar muscles
Loss of thumb adduction
Wasting of 1st webspace
Ulnar claw hand (hyperextension at metacarpal phalangeal joint, flexion at interphalangeal joint)
What does the straight leg test test for?
Radiculopathy
What would radial nerve palsy result in?
Wrist drop
Loss of sensation from 1st dorsal web space
What does musculocutaneous nerve palsy result in?
Reduced flexion at elbow
Loss of supination
What does median nerve compression result in?
Carpal tunnel syndrome
What does axillary nerve palsy result in?
Wastage of deltoid muscles
Loss of sensation in the badge area
Lesions where will cause problems with finger abduction?
T1
What does a +ve hoffmans sign indicate?
UMN lesion
Treatment for ocular myasthenia gravis
Pyridostigmine
What is mononeuritis multiplex?
A simultaneous or sequential involvement of individual non contiguous nerve trunks
Presentation of mononeuritis multiplex
Acute or subacute loss of sensory and motor function of individual nerves Asymmetric As disease progresses - confluent - symmetrical
What is mononeuritis multiplex hard to differentiate from as the disease becomes more advanced?
Polyneuropathy
What suggests GBS?
Progressive peripheral polyneuropathy with hyporeflexia
What is Saturday night palsy?
Compression of the radial nerve against the humeral shaft. Results in unable to extend wrist
Possibly due to sleeping on a hard chair with hand draped over the back
What is internuclear opthalmoplegia?
Occurs due to a lesion of the median longitudinal fasiculus, tract that allows to conjugate eye movements.
What does internuclear opthalmoplegia result in?
Impairment of adduction of ipsilateral eye
The contralateral eye abducts, however with nystagmus
Causes of internuclear opthalmoplegia
MS
Vascular disease
What are common precipitators of myasthenia crisis?
Beta blockers
Treatment of myasthenia crisis
Plasmaphresis and IV immunoglobulin
What does hoovers sign differentiate between?
Between organic and non organic leg weakness
What is the Jendrassik manouvre?
Compares a reflex with/without distraction e.g. clenching teeth
What does a positive rhombergs test indicate?
Sensory ataxia
