motor neuron disease Flashcards
motor neuron disease
a neurodegenerative disease characterized by progressive muscular paralysis reflecting degeneration of motor neurons
where does degeneration of motor neurons happen
- primary motor cortex
- corticospinal tracts
- brainstem
- spinal cord
heterogeneous or homogeneous
heterogeneous
hallmarks of MND
- rapidly progressive disorder of the nervous system
- does not affect sensory or autonomic systems
life expectancy from first symptom
4-5 years
MND causes degeneration in the UMN or LMN
both
motor neuron degeneration results in what symptom and dysarthria type
- muscle weakness
- flaccid or spastic dysarthria
how does spasticity cause muscle weakness
- reduced mobility leading to muscle atrophy from disuse
- impaired coordination, reducing overall strength and control
- fatigue
terms synonymous with MND
- amyotrophic lateral sclerosis (ALS)
- Lou Gehrig’s disease
typical onset
- as early as 20s
- usually early 60s
do women or men have a higher risk
women
prognosis
- no cure/remission
- no effective drug treatment
- 50% live < 3 years post-diagnosis
- 20% live 5+ years
peak incidence between ages ?
55 - 75 years
types of MND and %
- sporadic (90%)
- inherited (10-15%)
inherited familial cause
- genetic link
- 30+ genes identified
how to differentiate MND from PD/MS
never sensory changes in MND
MND general symptoms
- weakness
- slurred speech
- dysarthria
- muscle cramps and twitches
- weight loss
- emotional lability
- cognitive changes
emotional lability suggests ?
UMN involvement
which CN are resistant to degeneration
- CN III, IV, VI motor
- eye movements
emotional lability
- inability to control emotions
- crying/laughing but not sure why
fronto-temporal dementia (FTD) in ?% of MND
5-15%
subtypes of MND
- amyotrophic lateral sclerosis (ALS)
- progressive bulbar disease (PBP)
- progressive muscular atrophy (PMA)
- primary lateral sclerosis (PLS)
- Kennedy’s disease
amyotrophic lateral sclerosis (ALS)
- UMN + LMN
- weakness and wasting in the limbs
- life expectancy from symptom onset: 2-5 year
progressive bulbar disease (PBP)
- affects 1/4 of people diagnosed with MND
- UMN + LMN
- slurred speech and dysphagia
- life expectancy from symptom onset: 6 months-3 years
progressive muscular atrophy (PMA)
- rare
- LMN only
- life expectancy: 5+ years
primary lateral sclerosis (PLS)
- rare
- UMN only
- mainly weakness in lower limbs
- some clumsiness with hands and/or slurred speech
- life expectancy: normal (unless it develops into ALS)
Kennedy’s disease
- slowly progressive disorder of motor neurons
- genetic mutation
- rare form of muscular atrophy causing weakness
- only affects men (women can be a carrier)
- life expectancy: normal
? features are intrinsic to some subtypes of MND
cognitive
cognition changes in MND are associated with ?
- aggressive disease
- genetic mutation
- non-compliance
- caregiver burden
up to ?% of MND patients develop a cognitive impairment
50%
cognitive screening tests
- ALS Brief Cognitive Assessment
- ALS Cognitive Behavioral Screen
after MND diagnosis, patients should be screened for ?
cognitive and behavioral changes
cognitive changes
- executive function
- fluency
- language
- social cognition
behavioral changes
- apathy
- loss of sympathy
?% have concomital behavioral-variant FTD
13%
theories for causes of MND
- genetic
- traumatic
- toxic
- viral
- excitotoxicity
- oxidative stress
excitotoxicity
toxins interacting with glutamate receptors resulting in cellular calcium overload
oxidative stress
motor neuron damage from a cascade of reactions initiated
MND initial presentation
- stumbling
- foot drop
- loss of dexterity (increased conscious effort needed)
- weakened grip
- cramps
- voice changes
- fasciculations
- swallowing problems
average delay from onset of symptoms to diagnosis is ?
14 months (1/3 expected survival)
UMN symptoms
muscle weakness, stiffness, slowness of movement, tightness, spasticity
UMN features
- increased limb tone
- muscular weakness
- brisk tendon reflexes
- extensor plantar responses
LMN symptoms
muscle weakness, atrophy, cramping, and twitching
LMN features
- muscle wasting/atrophy
- fasciculations
- weakness with reduced or absent tendon reflexes
how to differentiate MND, spinal muscular atrophy (SMA), and Kennedy’s disease
fasciculations only occur in MND
possible sites of onset for MND
- limb/spinal
- bulbar
- respiratory
which site of onset has the worst prognosis
bulbar
limb/spinal onset will almost always progress to ? site of onset
bulbar
limb/spinal onset
- most common (60-70%)
- asymmetrical early symptoms
- upper limb presentation more common
- cramps/fasciculations
- heaviness or stiffness of legs
- often reported/stumbling
respiratory onset
- least common
- respiratory failure due to loss of bulbar, cervical, and thoracic motor neurons
- inspiratory muscles preferentially affected
- decrease in lung vital capacity to 50%
- initial report of mild dyspnea on exertion, morning sleepiness, headaches
why does respiratory onset manifest as morning sleepiness and headaches
lack of oxygen (retaining CO2)
respiratory onset assessments
- pulmonary function (PFTs)
- spirometry
- arterial blood gas (ABGs)
respiratory stage (not onset) features
- typically in advanced disease
- shortness of breath on exertion
- daytime sleepiness
- fatigue
- headache
- orthopnea
- weak cough/sniff
- nighttime restlessness/sweating
SOBOE
shortness of breath on exertion
orthopnea
shortness of breath when lying down that’s relieved by standing or sitting up
bulbar onset
- speech, swallowing, and OMA changes
- mostly bulbar as advanced stages not onset
- associated with: shorter survival, faster function decline, reduced QOL, increased support needs
symptoms of respiratory insufficiency in MND
- orthopnea
- SOBOE
- disturbed nighttime sleep
- excessive daytime sleepiness
- difficulty clearing secretions
- fatigue
- anorexia
- depression
- poor concetration/memory
- morning headaches
- nocturia
signs of respiratory insufficiency in MND
- increased respiratory rate
- use of accessory muscles
- paradoxical movement of abdomen
- decreased chest movements
- weak cough
- sweating
- tachycardia
- weight loss
- confusion
- papilloedema (rare)
nocturia
waking up more than once during the night because you have to pee
paradoxical movement of abdomen
chest wall or the abdominal wall moves in when taking a breath and moves out when exhaling
papilloedema
swelling of the optic discs due to intracranial hypertension
direct MND symptoms
- weakness/atrophy
- fasciculations
- spasticity
- dysarthria
- dysphagia
- dyspnea
- emotional lability
indirect MND symptoms
- psychological problems
- sleep disorders
- constipation
- drooling
- secretions
- pain (cramping)
- hypoventilation
are direct or indirect MND symptoms associated with a lower QOL
indirect
how to diagnose MND
- no one specific test, based on clinical findings
- Gold Coast Criteria (Shefner et al., 2020)
- El Escorial Criteria (1994)
Gold Coast Criteria
- newer set of simpler criteria for diagnosing MND
- presence of UMN and LMN dysfunction in 1+ body region
OR - signs of LMN dysfunction in 2+ body regions
El Escorial Criteria
- established by WFN (World Federation of Neurology), updated in 2000
- mixed UMN and LMN damage in the absence of other causes
indirect MND diagnostic tests
- needle electromyography (EMG; monitor the electrical signals in 1 muscle and look for irregular activity)
- nerve conduction studies (look at efficiency)
- chest x-ray
- autoantibody screen
- thyroid function tests
- creatine kinase
- biochemical screen (look at genes for familial link)
- full blood count
diagnostic materials for bulbar signs or MND
- cranial nerve exam
- needle EMG (genioglossus, SCM, trapezius)
- clinical MRI of bulbar regions
- auditory perceptual ax of dysarthria
- frenchay dysarthria ax
- videofluoroscopy swallowing exam
- EAT-10
- 3oz swallow test
- voluntary cough
outcome measures/rating scale test
- ALSFRS (Amyotrophic Lateral Sclerosis Functional Rating Scale)
- areas relevant for SLTs: speech, salivation, swallowing
MND treatment
- MDT
- mostly symptomatic relief
- individualized alleviation of symptoms/complications
- rizuole
- based on excitotoxicity theory of MND pafthogenesis
riluzole
- MND treatment
- primary line of defense
- prolongs median survival from 11.8 months to 14.8 months
newer drug treatments for MND
- ellorarxine
- tofersen (SOD1 gene)
- edaravone
- nuedexta
SLT input
- speech/communication
- swallowing
- sialorrhea (drooling)
dysarthria/dysphagia signs in MND
- flaccid or spastic
- strangled voice quality (if spastic)
- vocal cord paresis
- soft palate involvement
- dysphagia for solids and liquids
- nasal regurgitation
- choking episodes
- weak cough/throat clearing
- drooling
- tongue fasciculations
dysarthria in MND is associated with….
low mood, withdrawal from activities, social isolation
LMN MND
- bulbar palsy
- flaccid dysarthria
- nasal speech
- nasal regurgitation
- absent jaw jerk
- reduced/absent gag reflex
- lingual atrophy/fasciculations
UMN MND
- pseudobulbar palsy
- spastic dysarthria
- emotional lability
- brisk jaw jerk
- hypersensitive gag reflex
- shrunken immobile tongue
which therapeutic approach to MND (and why)
- compensatory approach
- to optimize intelligibility
speech subsystems and typical impairments in MND
- respiration (poor respiratory support for speech short phrases)
- phonation (strained-strangled voice, low pitch, weak breathy voice, audible inspiration, low volume)
- articulation (imprecise consonants, distorted vowels, rate and range of articulators)
- prosody (monopitch, monoloud, reduced stress)
- resonance (hypernasality)
dysarthria management
- education
- compensation
- AAC
- voice/message banking
AAC considerations
- upper limb function
- literacy
- computer confidence
- cognition
- socially acceptable
- timing
- decline
- prognosis
types of AAC switches
- click
- air pad
- bulb
- puff
- foot
- eye blink
goal of dysphagia management for MND
- safe and efficient oral intake of food and fluids
- maximum independence
- emphasis on patient’s wishes and QOL
swallow management in MND usually involves use of ? strategies (and why)
- compensatory
- active exercises simply cause fatigue
which recommendations can SLTs make
- education/written info
- volume control beaker
- compensatory strategies (chin down, double swallow)
- diet modification
- list of foods to avoid
- saliva management
- discussion with MDT re: long term nutritional management (i.e. PEG insertion)
- EMST
what is important to consider with PEG insertion
- site of onset
- respiratory onset requires a quicker PEG insertion because of limited respiration
tube feeding in MND
- should not be seen as crisis intervention when the patient is malnourished and dehydrated
- ideally at 5% weight loss and before respiratory involvement
- consider respiratory reserve
PEG does not mean ?
NPO (aim for some form of oral intake for QOL)
sialorrhea treatments in MND
- behavioral changes
- education
- anticholinergic meds
- botox
- radiation (fewer side effects but shorter duration than botox)
- portable suctioning devices
anticholinergic medication function
block the receptors that stimulate saliva production
