Motor neurone disease Flashcards
What is the definition of Motor Neurone disease
umbrella term that encompasses a variety of specific diagnoses. It is a cluster of degenerative disease characterised by axonal degeneration of neurones in the motor cortex, cranial nerve nuclei and anterior horn cells.
What is Amyotrophic lateral sclerosis:
- The familial form is associated with mutations in superoxide dismutase(SOD1)
- UMNsigns: predominantly affects the corticospinal tracts
- LMNsigns: also affects anterior horn cells
- Overall,mixed UMN/LMNsigns may be seen
- UMN + LMN
- most common
What is Progressive muscular atrophy:
- Primarily the muscles of talking and swallowing
- LMN signs: predominantly affects the anterior horn cells
- Best prognosis
- LMN only
What is Primary lateral sclerosis:
- Least common
- Loss of Betz cells in motor cortex
- UMNsigns: predominantly affects the corticospinal tracts
- UMN only
What is Progressive bulbar palsy:
- Affects the suprabulbar nuclei and cranial nerves, producing speech and swallow issues
- Worst prognosis
- LMN only
Epidemiology of MS
- Rarely presents before 40 years old. The average age of onset of MND is 60 years old
- M>F
- Often fatal in 2-4yrs
- 5000 in UK
- 10% of people live for 10 years
RFs for MND
- Advancing age
- Male gender: 1.2 to 1.8 times more likely to develop MND
- Family history: familial in 5% of cases and the SOD1 mutation is implicated
- Smoking: currently a ‘probable’ risk factor for MND
- Exposure to heavy metals and certain pesticides
What is the pathophysiology of MND?
- Motor neurone disease is a progressive, ultimately fatal condition where the motor neurones (both upper and lower) stop functioning. There is no effect on the sensory neurones and patients should not experience any sensory symptoms.
- There is a genetic component and many genes have been linked with an increased risk of developing the condition.
Signs of MND
- Mixed UMN and LMN signs
- Spastic paraparesis with brisk reflexes
- Upgoing plantar responses
- Fasciculations (twitches in the muscles) especially on the tongue
- Dysarthria and dysphagia: particularly in progressive bulbar palsy
- Muscle wasting: particularly of small hand muscles and tibialis anterior
- Reduced tone
- Limb onset
- Bulbar onset
- Respiratory onset
Symptoms of MND
- Progressive weakness often first noticed in the upper limbs
- Clumsiness
- Fatigue
- Falls
- Speech and swallow issues: particularly in progressive bulbar palsy
- respiratory problems - a lot of these
Symptoms that are absent in MND
No sensory abnormalities
No extraocular involvement
No cerebellar involvement
Sphincter dysfunction is rare and would only present as a late feature
Abdominal reflexes are usually preserved
Clinical diagnosis of MND
- Definite: LMN + UMN signs in 3 regions
- Probable: LMN + UMN signs in 2 regions
- Probable with lab support: LMN + UMN signs in 1 region, or UMN sign in more than 1 region + electromyography (EMG) shows acute denervation in more than 2 limbs
- Possible: LMN + UMN signs in 1 region
- Suspected: LMN OR UMN sign only - in 1 or more regions
Investigations to rule out other pathology?
- Electromyography:in MND there will be evidence of fibrillation potentials
- Nerve conduction studies:may show modest reductions in amplitude
- MRI spine:imaging can help exclude spinal pathology which may mimic MND, such as cervical cord compression and myelopathy
- Lumbar puncture: to exclude inflammatory causes
- Pulmonary function tests:patients with MND are at risk of respiratory failure
Differential diagnosis
- Multiple sclerosis
- Polyneuropathies
- Myasthenia gravis
- Diabetic amyotrophy
- Guillain-Barre syndrome
- Spinal cord tumours
- Polio
- Parkinosns
- FTD
1st line management of MND
- Riluzole:prolongs survival by 2-4 months; it is thought to protect motor neurons from glutamate-induced damage
- Respiratory support:patients with reduced FVC can use non-invasive ventilation at home, usually BiPAP; prolongs survival by 7 months
- Multi-disciplinary specialist care
