MND 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
Supportive treatment for MND?
- Antispasmodics: such as baclofen
- Analgesia
- Feeding support: many patients require nutritional support, often with PEG tube
- Speech and language therapy
- Physiotherapy
- Advanced directivesto document the patients wishes as the disease progresses
- End of life careplanning
Complications of MND
- Aspiration pneumonia andbronchopneumonia
- Respiratory failure: often occurs in advanced disease when respiratory muscles have been affected
- Dementia
- Cognitive problems
- Parkinsonism
Prognosis of MND
Prognosis is variable and depends on the pattern of disease, with progressive bulbar palsy associated with the worst prognosis.
Most patients die within 3 years from the onset of their symptoms.
Poor prognostic factors include progressive bulbar palsy, old age and poor respiratory function. The majority of patients die from respiratory complications.
UMN lesion
- Hypertonia; rigidity + splasticity (rigid w/ movement)
- Hyperreflexia
- No fasciculation
- Babinksi +ve
- Arms: Flexor > Extensors
- Legs: Flexors < Extensors
LMN lesion
- Hypoturia (flaccal) + muscle wasting
- Hyporeflexia
- Fasciculations
- Babinski -ve
- generally lower power
If you see mixed UMN + LMN signs what should you think?
MND
What does MND never affect
Eye muscles > MS+ MG
Sensory function > MS + polyneuropathies
Organisation of movement
1.Idea of movement - assosciation carexes, pre- motor cortex
2. Activation of UMNs in motor cortex
3. Impulse via corticopsinal tract
4. Modulation by
- cerebellum > fine tuning
- BG > Green signal to move
5. Movement + somatosensory info obtained by sensory tracts
UMN symptoms
- weakness , pyramidal
- spasticity
LMN symptoms
- wasting
- weakness
- fasciculations - spontaneous firing of the motor unit
why does spascticity occur
umn provides a stop signal to lmn
loss of umn thus no stop signal so more activation of lmn
what are fasiculations
sponatenious firing of motor unit
Bulbar symptoms
- Progressive, relentless
- Dysarthria
- Dysphasia
- Jaw spasms
- Emotional lability
- Oropharyngeal muscles
What is unaffected in ALS
Oculomotor and Onuf’s nucleus motor neurones that are unaffecetd
A 51-year-old man presents with progressive weakness over the past couple of months. The weakness is mainly affecting his legs which results in him struggling to climb his stairs at home. The weakness is also now affecting his right hand and has led to him dropping objects. On examination, you note thenar muscle atrophy and fasciculations. There is also increased tone in the lower limbs and hyperreflexia of the knee and ankle jerks. No sensory deficit is identified. What is the most likely diagnosis?
Spinal amyotrophic lateral sclerosis
