motor neuron disease Flashcards
nm disease
peripheral Polyneuropathy
Peripheral
neuropathy
nm junction
Myasthenia
gravis
Lambert Eaton Syndrome
primary muscle disorder
muscular dystrophy
mitochondrial myopathies
mixed U / LMN
MN disease
motor neuron disease
Progressive neurodegenerative disease
Insidious onset of painless, progressive weakness
Characterised by progressive loss of motor neurons in the cortex, brain stem and spinal cord, leading to worsening paralysis of voluntary muscles
Unknown aetiology
Genetics: complex, 5-10% familial MND
epidemiology
Commonest neurodegeneration of young and middle aged adults
Incidence: 0.6-2.6 / 100,000
Approximately 200 people with MND in Ireland at any one time
Age of onset 47-63 years in most cases, but can occur at any age
Unknown cause
Fatal disease
Median survival 2.5-5y from diagnosis 40% survive >5y, 10% >10y
Survival depends on distribution of symptoms: bulbar onset median
survival 141 days, limb onset 605 days
early symptoms
Variable, depends on where the loss of motor neurons starts
Most common symptoms: Clumsy hand Slurred speech / dysarthria Shoulder weakness Foot drop / tripping Difficulty walking (spasticity) Decreased endurance Fasciculation
signs and distribution
Upper Motor Neuron Signs
Slurred speech
Altered emotional control Spasticity
Slurred speech Hyperreflexia Reduced dexterity
Lower Motor Neuron Signs
Weakness Muscle atrophy Fasciculations Cramping Areflexia
bulbar signs
Dysphagia Slurred speech Loss of speech Weak cough SOB
Impaired saliva management
Aspiration
“Spinal” Signs Limb weakness Spasticity Clumsy hand Foot drop
Other symptoms
Fatigue Weight loss Pain
Fronto-temporal dementia
Types of MND
amyotropic
66%
UMN + anterior horn cells
progressive muscular atrophy
7.5%
LMN
involvement only
progressive bulbar palsy
Bulbar +pseudobulbar involvement
primary lateral sclerosis
UMN signs only
diagnosis
No single test or biomarker
Characteristic clinical findings, supported by
investigations, with exclusion of differentials
EMG: widespread denervation / reinvervation, conduction block, fibrillation
NCS: Normal sensory responses, no conduction
block
MRI: to exclude other disorders (usually normal)
Difficult diagnostic process, typical delay of 9-15 months
Common to have “misdiagnoses” along the way,
e.g. cervical / lumbar radiculopathy
full blood count
ESR CRP
creative kinase is elevated
Vit B12 and folate
muscle biopsy
lumbar puncutre
HIV and lyme serology
El escorial criteria for diagnosis
Definite ALS
Presence of upper motor neuron and lower motor neuron signs in the bulbar region and at two of the other spinal regions
Probable ALS
Presence of upper motor neuron and lower motor neuron signs in at least two regions with upper motor neuron signs rostral to lower motor neuron signs
Probably ALS, laboratory results supported
Presence of upper motor neuron and lower motor neuron signs in one region with evidence by EMG of lower motor neuron involvement in another region
Possible ALS
Presence of upper motor neuron and lower motor neuron signs in one region or upper motor neuron signs in two or three regions, such as monomelic ALS, progressive bulbar palsy and primary lateral sclerosis
prognostic factors
site of onset: better - limbs
worse prog bulbar/ resp
diagnostic delay better- longer
worse - shorter
family history C9orf72 gene
rate of progression
faster - better
slower - worse
psychological factors - worse - distress
fronto-temporal dementia - no FTD
worse + FTD
weight low BMI / smoking = worse prognosis
care model - access to specialist MDT - better
worse - non-specialist care
pharm
Riluzole Increases survival by (median) 4.2 months Mechanism not fully understood: Antiglutaminergic modulation? Mitochondrial function? Fat metabolism? Calcium or sodium channel function? Prescribed early in Beaumont
speech difficulties
Dysarthria – Anarthria
Due to flaccid or spastic muscles of speech
Decreased respiratory function
Speech strategies Alphabet board “Lite writer” Writing Texting Eye Gaze / Eye Tech software Voice banking
swallowing difficulties
45% of Irish patients have difficulty swallowing
81% have difficulty at time of death
SLT & Dietitian assessment – videofluroscopy
Swallowing techniques
Thickened fluids / modified diet
RIG / PEG – if appropriate – complex decision: rationale:
Declining weight (>10% BW)
Increased time spent at meals
Increasing dysphagia
Quality of life
Respiratory function FVC>50%, SNIP >40cm H2O
Tolerates NIV
resp dysfunction
Respiratory failure most frequent cause of death
People with MND most often have healthy lungs!
Respiratory problems occur due to loss of bulbar, cervical and
thoracic motor neurons
Inspiratory muscles preferentially affected → Hypoventilation → Impaired gas exchange
Weak cough results from weakness in inspiratory muscles, bulbar function and expiratory muscles
Significant impact on Quality of Life
secondary problems
Atelectasis Secretion retention Fatigue due to coughing ineffectively Pneumonia Disuse atrophy Shortening of musculature Chest wall stiffness Reduced lung compliance
medical mgmt for resp problems
Tracheostomy
Common in some countries
Prolongs survival but can result in poor QOL
Generally not in Ireland
- NIV in form of NIPPV
Decision based on overnight pulse oxymetry, early morning ABGs, SNIP and presenting symptoms
Reduces work of breathing
Improve gas exchange, exercise tolerance, sleep quality
Prolongs survival - Use of meds to decrease secretion production
