MND Flashcards
What is motor neurone disease ?
- This is a cluster of major degenerative diseases charaterised by selective loss of neurons in the motor cortex, cranial nerve nuclei, and anterior horn cells
- Upper and lower motor neurons are affected
- There is no sensory loss or sphincter distrubance thus distinguishing NMD from MS and polyneuropathies
- MND never affects eye movements, distinguishing it from myasthenia gravis
- No cerebellar signs
What are the 4 main types of motor neuron disease (MND)?
- ALS (amyotrophic lateral sclerosis)
- Bulbar onset MND or Progressive bulbar palsy (PBP)
- Progressive muscular atrophy (PMA)
- Primary lateral sclerosis (PLS)
What are the general symptoms which suggest MND ?
- Muscle weakness and potentially problems with speech, swallow & breathing
- Upper and/or Lower motor neurone signs
- Focal onset and continuous spread, finally generalized paresis
Doesnt affect extra-ocular eye muscles nor cerebellum & doesnt cause sensory signs/symptoms
What may patients with ALS go on to develop ?
Cognitive dysfunction may occur and 5-15% of patients develop dementia, usually of frontotemporal type.
underpinned by discovery of C9ORF
What is the most common subtype of MND ?
ALS
Is MND more commonly familial or sporadic ?
90 % ‘sporadic’ and 10% ‘familial
What is the peak age of incidence of MND?
- Sporadic MND peaks at the ages of 50-75 years and declines after the age of 80
- It is very rare before 40yrs old
What are the upper and lower motor neuron signs of MND?
Usually it is the mix of lower and upper motor neuron abnormalities in the absence of sensory disturbances. Cognitive impairment may be part of the presentation (FTD). Ask about cramps, fasciculations, foot drop, family history, behavioural changes
LMN signs: fasciculations (including tongue), wasting in groups outside a single myotome.
UMN signs: increased tone, clonus, loss of dexterity, brisk tendon reflexes (or preserved TR in wasted and / or fasciculating muscles), Babinski sign
Describe ALS
- It is due to loss of motor neurons in the motor cortex and in the anterior hornn cells it presents as a combination of upper motor neuron (UMN) and lower motor neuron (LMN) symptoms and signs
- Can start in limb, axial, bulbar, or respiratory muscles and then generalises relentlessly, causing progressive disability and ultimately death, usually from respiratory failure.
- Usually initially presents with either:
Limb onset - by far the most common.
Bulbar onset - 20% of cases.
or Respiratory onset - the least common.
Describe the ways in which ALS can present
Patients or their families often notice problems occurring in one or more of the patterns below:
Limb weakness - usually affects the upper limbs:
- Causes patients to drop objects or have difficulty manipulating objects with one hand (turning keys, writing and opening bottles).
- Wrist drop, stiffness, weakness or cramping of the hands may also occur.
- Patients may also notice a change in the appearance of their hands (due to wasting of the intrinsic muscles).
- Fasciculations and wasting of the muscles of the limbs
However, occasionally problems in the leg or legs may occur:
- Foot drop (early).
- Gait disorder.
- A sensation of heaviness of one or both legs.
- A tendency to trip.
- Difficulty in rising from low chairs and climbing stairs.
- Excessive fatigue when walking.
- +ve babinskis sign
Bulbar onset:
- The first sign is usually slurring of the speech (impaired tongue movement).
- Wasting and fasciculation of the tongue.
- Dysphagia (usually a late feature with significant speech difficulties).
- Accompanying emotional lability (inappropriate laughing or crying) - as with pseudobulbar palsies.
- Other symptoms are difficulty eating, drooling, dysarthria, dysphonia, choking events with meals, nasal regurgitation of fluids or pulmonary aspiration.
Respiratory onset can present with:
- Dyspnoea and orthopnoea.
- Clinical features resulting from hypoventilation overnight (for example, waking, unrefreshing sleep, hypersomnolence and early morning headaches).
Describe the presentation of progressive bulbar palsy subtype of MND
This is when CN’s IX- XII are only affected so it only causes the bulbar symptoms mentioned in ALS symptoms, it then goes onto to progress into ALS
What is the classic sign seen in the hand suggestive of ALS ?
Preferential wasting of thenar group is a typical pattern of atrophy seen in ALS
Describe the presentation of progressive muscular atrophy subtype of MND
- This is due to anterior horn cell lesions only so only LMN signs seen
- Distal muscle groups are affected before proximal
Describe the presentation of primary lateral sclerosis subtype of MND
- This is due to loss of betz cells in the motor cortex and as a result there is mainly UMN signs no LMN signs
- It results in marked spastic leg weakness and pseudobublar palsy
- No cognitive decline occurs in this type
Describe a bulbar palsy
This is disease of CN’s IX-XII
Signs are of LMN lesion of the tongue and muscles of talking and swallowing:
- Flaccid, fasiculating tongue (like a sack of worms)
- Jaw jerk normal or absent
- Speech is quiet, hoarse or nasal
What is the diagnostic criteria for ALS ?
- Definite = lower and upper motor neuron signs in 3 regions
- Probable = lower and upper motor neuron signs in 2 regions
- Probable with lab support = lower and upper motor neuron signs in 1 region, or upper motor neuron signs in 1 region and EMG findings showing acute denervation in > or equal to 2 limbs
- Possible = upper and motor neuron signs in 1 region
