Motor Neuron DIsease Flashcards
What is MND?
group of neurological disorders that destroy MNs (cells that control skeletal muscle activity such as walking, breathing, speaking and swallowing.
Causes progressive degeneration of UMNs and LMNs.
What area of the NS is affected?
UMNs in brain (motor cortex) and LMNs (spinal cord and brainstem).
Primarily affects CNS but LMNs extend into PNS to connect with muscles (weakness and atrophy in muscles = PNS)
Epidemiology of MND (Van Es, 2017)
- 3rd most common adult onset neurodegenerative disorder
- Incidence: 2.6-3 cases per 100,000
- Prevalence: 7 per 100,000
- Onset: commonly in early 60s but can start asearly as 20s
- Male : Female risk = 1 in 350 : 1 in 400
- 275 cases registered with IMNDA
Cause of MND
- Unknown: likely to be sporadic
- Envir, viral and other factors may play a role:
- genetics: 10% familial SO gene
- traumatic: mechanical/electrical
- toxic: agri chemicals or heavy metals
- viral
- excititoxicity: toxins interacting with glutamate (pathologically high levels) receptors resulting in cellular calcium overload
- oxidative stress: imbalance of free radicals and antiox in body = cell damage - MN damage by cascade of events
- ? too much exercise/training regime of athletes
Course of MND
- Rapidly progressive
- Initial presentation: stumbling, foot drop/drag, loss of dexterity, weakened grip, cramps, voice changes, fasciculations, swallowing - signs tend to be asymmetrical
- Bulbar presentation tends to be first symptom
Early stage: mild muscle weakness, twitching, cramping, often affecting one limb. ADL mainly unaffected
Middle Stage: weakness spreads to multiple muscle groups, affecting fine motor skills, walking and balance. Speech and swallowing difficulties may arise. May need mobility aids
Late stage: severe paralysis and loss of independence. May need wheelchairs, full-time care, AAC and feeding support. Resp. complications become life-threatening
Pneumonia tends to be cause of death.
Prognosis of MND
- No cure/remission
- No effective drug tx
- Lifetime risk: 1 in 2000
- 1/2 live less than 3 years after diagnosis
- 20% live 5+ years
- Peak incidence between 55-75 (slight male predominance)
Cognitive/behavioural changes in MND
- 60% personality change, irritability, obsessions, poor insight and pervasive deficits in frontal executive tests.
- Associated with aggressive disease, genetic mutation, non-compliance and caregiver burden
Cognition:
- affects executive function, fluency, language and social cognition
- up to 50% develop some sort degree of cognitive impairment
- Screening test: ALS Brief Cog Ax/ALS Cog Behavioural Screen
- 5-15% have fronto-temporal dementia
Behavioural features:
- apathy
- loss of sympathy
Signs and symptoms of MND
UMN:
- muscle weakness, stiffness, slow movements, tightness or spasticity
- increased limb tone, brisk tendon reflexes, extensor plantar responses
LMN
- muscle weakness, cramping and twitching
- muscle wasting/atrophy, fasciculations, weakness with reduced or absent tendon reflexes
Features:
- don’t affect sensory/autonomic systems or sphincter
- CN III, IV, VI motor resistant to degeneration (eye movement)
- Emotional lability (UMN)
Subtypes of MND
- Amyotrophic Lateral Sclerosis: most common, UMN and LMN, weakness and wasting in limbs
- Progressive Bulbar Palsy: 1/4, UMN and LMN, slurred speech, difficulty swallowing
- Progressive Muscular Atrophy: small proportion, mainly LMN, early symptoms = hand clumsiness/weakness
- Primary Lateral Sclerosis: rare, only UMN, weakness in lower limbs (+ hand clumsiness/speech problems), could progress into ALS
Kennedy’s Disease: not subtype of MND but similar traits. Slowly progressive MN disorder caused by gene mutation, only affects men
Diagnosis of MND
- No one disease-specific test: based on clinical findings, hard as MND is a heterogenous group of disorders
- Gold Coast Criteria (Shefner et al., 2020): sign of UMN and LMN dysfunction in one region or signs of LMN dysfunction in 2+ regions.
- El Escorial Criteria (1994): diagnosis can be made if evidence of mixed UN and LMN damage in absence of other causes.
Diagnostic tests for MND
- Needle Electromyography (EMG)
- Nerve conduction studies
- Chest X-ray
- Autoantibody screen
- Thyroid function tests
- Creatine kinase
- Biochemical screen
- Full blood count: ESR, CRP, FBC, LFTs, vitamin B12 and folate, thyroid function tests, serum protein electrophoresis, CK, electrolytes, glucose, ACE
Medication for MND
- Symptom-management
- Riluzole: prolongs median survival from 11.8 months to 14.8 months (quality vs quantity). Based on excitotoxicity theory of MND pathogenesis.
- New drug tx: ellorarxine, tofersen (SOD1 gene), edaravone approved in Japan, nuedexta (?improves bulbar symptoms)
Rating scales/outcome measures for MND
ALS Functional Rating Scale (Cedarbaum et al., 1999)
SLT Assessment: speech and communication in MND
- Dysarthria prevalence: 20% at diagnosis, 80% in advanced stage
- Mixed dysarthria: spastic (UMN) and flaccid (LMN)
Subsystems affected:
- Respiratory: poor resp. support
- Phonation: strained, strangled, low pitch, weak, breathy, low volume
- Resonance: hypernasality
- Articulation: imprecise consonants, distorted vowels, reduced range and rate
- Prosody: monopitch and loudness, reduced stress
Patient-reported: nasal, slurred, weak, breathy, strained, SOB, difficulty managing saliva
SLT Assessment: swallowing in MND
- Clinical evaluation: case history questions, CSE
- Instrumental: VF, FEES
- Common issues: dysphagia, nasal regurgitation, choking, weak cough/throat-clearing, drooling, fasciculations
SLT Intervention: dysarthria management in MND
- Education
- Compensatory strategies
- AAC: IMNDA support, eye-gaze. COnsider timing, literacy, cognitive status and physical impairments.
- Voice/Message Banking: RMN.ie, IMNDA, MND Association
*No evidence for OMEs
SLT Intervention: dysphagia management in MND
- Goal: safe and efficient oral intake with maximum independence, respecting preferences and QOL
- Compensatory strategies: chin tuck, double swallow, volume control beaker, avoiding high-risk food
- Diet modifications
- Equipment and support: PEG vs RIG insertion (RIG for those with respiratory issues)
- EMST: swallow and cough improvement but won’t reverse. Proactive intervention rather than purely palliative approach
Saliva management in MND
- Behavioural adjustments and education
- Pharmacological: anticholinergic meds e.g. hyoscine patch
- Botox
- Radiation Therapy
- Portable Suctioning Device
MND Associations and Charities
- IMNDA
- MND Association (UK)
- ALS Association (US)
- Dysphagia Café
3 sites of onset:
- Limb/spinal
- Bulbar
- Respiratory
Limb or
Spinal Onset
- Most common pattern
- 60-70% of cases
- Early symptoms asymmetrical
- Upper limb presentation more common
- Cramps/fasciculations
- Heaviness or stiffness of legs
- Often reported/stumbling
Respiratory
Onset
- Least common pattern of presentation
- Repiratory failure due to loss of bulbar, cervical and thoracic motor neurones
- Inspiratory muscles preferentially affected
- Decrease in lung vital capacity to 50%
- Initial report of mild dyspnoea on exertion
- Other symptoms include morning sleepiness,, headaches
- Pulmonary Function Tests (PFT’s) (spirometry; SNIP; ABG’s; TOSCA)
Bulbar Onset
- Speech, swallowing and oro-motor changes
- 30% cases at time of diagnosis & 80% bulbar symptoms at advanced stages
- Associated with: shorter survival, faster functional decline, reduced QOL, increased MND support needs.
