Muscle and Nerve Disease Flashcards
what are the symptoms of a muscle disease?
weakness of skeletal muscle- limb weakness or intercostal/diaphragmatic muscles= impaired respiratory function or swallowing issues, weakening of cardiac muscle leading to heart problems, muscle pain or cramps, myoglobinuria (urine turned a very dark colour as lots of myoglobin= muscle breakdown product)
what are the signs of muscles disease?
pure motor signs and not associated with sensory signs, muscle tenderness, muscle wasting or enlargement
what are the 2 main groups which can cause muscle disease?
congenital/genetic or acquired
what are some congenital/genetic muscle diseases?
contractile eg congenital myopathies, structural eg muscular dystrophies, coupling eg channelopathies, enery eg metabolic myopathies
what are contractile- congenital myopathies?
often young onset disease with weakness and it relatively static throughout someones life
what are structural- muscular dystrophies?
tend to be severe and progressive, young onset but progress quickly with muscle weakness and are often life shortening
what are coupling- channelopathies?
some can give paroxysmal disorders eg paroxysmal weakness which comes on vert quickly and lasts for minutes or hours and then resolves spontaneously
what are energy- metabolic myopathies?
genetic deficits in many of the enzymes that generates ATP or the breakdown of glycogen and FA or genetic defects of the mitochondria and these will cause pain on exercise
what are some acquired muscle disorders?
electrolyte disturbances, endocrine, autoimmune inflammatory muscle disease, iatrogenic
how do electrolyte disturbances cause muscle disorder?
especially very high to very low levels of K+ can give you muscle weakness
how do endocrine disorders cause muscle disorder?
eg thyroid, adrenal or vitamin D changes can cause muscle weakness
how do autoimmune inflammatory muscle disease cause muscle disorder?
2 types= polymyositis (inflammation of the muscle alone) and dermatomyositis (skin and muscles causing rash and muscle weakness), any age, generally acute onset and generate pain, weak muscles and characteristic rash of DM on face or hands- high CK and autoimmune nature so look for autoantibodies- DM often associated with underlying tumour (muscle weakness= paraneoplastic), EMG for diagnosis and immunosuppression (steroids or steroid sparing agents like azathioprine) for treatment
what medication can cause muscle disorders?
steroids and statins
what is a disorder of the NMJ?
myasthenia gravis
what is myasthenia gravis?
an autoimmune condition that causes muscle weakness that gets progressively worse with activity and improves with rest
who does myasthenia gravis usually affect?
women under 40 and men over 60
what is strongly linked to myasthenia gravis?
thyomas= tumours of the thymus gland
what is the pathophysiology of myasthenia gravis?
it is an autoimmune process associated with the ACh receptor antibody which blocks the ACh receptor in the NMJ so stopping ACh from activating the receipts and generating muscle contraction causing reduced muscle activity
how does myasthenia gravis present?
fatiguable weakness ie worse with muscle use and improves with rest, typically minimal in the morning and worst at the end of the day
where do symptoms of myasthenia gravis usually present and what are they?
most affect proximal muscles and the small muscles of the head and neck causes diplopia (muscles of eye movement), ptosis (eyelid muscles), weakness of facial movements, difficulty swallowing, chewing and slurred speech
how is a diagnosis of myasthenia gravis made?
testing directly of ACh-R antibodies or anti-MuSK antibodies in the blood
what other investigations could we go?
CT or MRI of the thymus gland to check for a thymoma and an edrophonium test if in doubt about the diagnosis - edrophonium blocks enzymes which breakdown ACh, so ACh at NMJ increase which relieves weakness and confirms diagnosis of myasthenia gravis
what are the treatment options for myasthenia gravis?
cholinesterase inhibitors increase the amount of ACh in the NMJ so improve symptoms, immunosuppression supresses production of antibodies= steroids, thymectomy (even without thymoma) improves symptoms
what are possible causes of peripheral nerve disease?
root disease, lesion on individual peripheral nerve, generalised peripheral neuropathy
what is a root disease?
damage to the nerve root as it comes out of the foramen of the vertebrae and the most common cause of this is degerative disc disease
what is a lesion of an individual peripheral nerve?
compression or entrapment of the nerve= neuropathy or vasculitis of blood supply of a nerve with damage to the nerve, multiple nerves affected= mono neuritis multiplex
what is a generalised peripheral neuropathy?
affects motor and sensory parts of the nerves and can be one more than the other or equally and generally has autonomic features too - can be axonal or generalised peripheral neuropathy
what is Guillain Barre syndrome?
an acute paralytic polyneuropathy that affects the PNS and causes acute, symmetrical, ascending weakness and can also cause sensory symptoms
what usually causes Guillain Barre syndrome?
an infection and is particularly associated with campylobacter jejune, cytomegalovirus and EBV
what is the pathophysiology go Guillain Barre syndrome?
occurs due to a process called molecular mimicry where B cells of the immune system against antigens on the pathogen that causes the preceding infection also match the protein on the nerve cells
what is the presentation of Guillain Barre syndrome?
symmetrical ascending weakness (starting at the feet and moving up the body), reduced reflexes, maybe peripheral loss of sensation or neuropathic pain and may progress to facial nerve weakness
what is the clinical course of Guillain Barre syndrome?
symptoms start usually 4 weeks of the preceding infection, symptoms in the feet and upwards
how is Guillain Barre syndrome diagnosed?
made clinically using the Brighton criteria but can be supported by nerve conduction studies and lumbar punctures for CSF (raised protein with normal cell count and glucose)
how is Guillain Barre syndrome treated?
IV immunoglobulins, plasma exchange, supportive care and VTE prophylaxis and if respiratory failure then intubation and ventilation
what are the sensory symptoms?
loss of sensation, abnormal sensation and pain
what are the motor symptoms?
muscle thinning if prolonged and weakness= common
what are the autonomic symptoms?
skin discolouration or loss of hair, postural hypotension and bladder and bowel problems
what are the sensory signs?
reductions and alterations in light touch, temperature, joint positions and vibration sensations
what are the motor signs of peripheral nerve disease?
LMN signs
what are the LMN signs?
muscle wasting, fasciculations, loss of muscle tone, weakness and reduced or loss of tendon reflexes
describe the distribution of root disease.
weakness in the muscles that the nerve root supplies= myotomal weakness and loose sensation in the dermatome supplied by that nerve root
what is motor neurone disease?
an umbrella term for a variety of specific diagnoses, a progressive fatal condition where the motor neurones stop functioning, there is no effect on the sensory neurones
what is the most common type of MND?
amyotrophic lateral sclerosis (AML) and is well-known as this is what Stephen Hawking had
what is the second most common type of MND?
progressive bulbar palsy which affects primarily the muscles of talking and swallowing
what is the pathophysiology of MND?
progressive degeneration of both upper and lower motor neurones but not sensory neurones
how does MND present?
typically a late middle-aged man with progressive weakness of muscles throughout the body, often in upper limbs first, increased fatigue when exercisin, dysphasia and clumsiness, signs of UMN and LMN disease
what are the signs of UMN disease?
increased tone or spasticity, brisk reflexes and upping plantar reflex
how is MND diagnosed?
clinical presentation and excluding other conditions which can cause motor neurone symptoms
how is MND managed?
no effective treatments for halting or reversion the progression of the disease- riluzole (glutamate antagonist)= extends survival in AML by a few months, NIV (non-invasive ventilation) is also used to support breathing at night
what do we need to do due to the poor prognosis of MND?
effectively break the bad news and plan end of life care
