Motor Neurone Disease
Motor neuron diseases are a heterogeneous group of disorders characterized pathologically by death of motor neuron cells ( Thomas T.Warner , Practical Guide to Neurogenetics , 2009 )
The red flag tool can be assessed via https://static.mndassociation.org/app/uploads/2013/10/19140141/red-flags-final-2.pdf
Subtypes –MND classification is based on those affecting primarily the UMNs , those affecting the LMNs and those affecting both
Amyotrophic lateral sclerosis or Lou Gehrig’s disease- Involvement of upper , lower and brainstem motor neurons 70 % of cases of adult onset Fatal disorder – progressive skeletal muscle weakness and wasting or atrophy ( hence amyotrophy ) , spasticity and fasciculations due to degeneration of UMNs, LMNs –> eventual respiratory paralysis Most cases sporadic ( 5-10 % familial ) Median survival 3 yrs
Primary lateral sclerosis-Rare -idiopathic neurodegenerative disorder Pure UMN -predilection for lower limb dis onset Slower dis progression and better prognosis
Progressive bulbar palsy-Disorder of motor nuclei in medulla Atrophy and fasciculations of the lingual muscles , dysarthria and dysphagia May eventually lead to widespread symptoms typically seen in ALS
Hereditary spastic paraparesis-Familial spastic paraplegia or Strumpell-Lorrain disease slowly progressive spastic paraparesis
Spinal muscle atrophy X-linked spinobulbar muscular atrophy ( SBMA ; Kennedy disease ) Postpolio syndrome
Epidemiology- All motor neurone diseases are rare Peak age of onset 55-75 yrs – men affected more commonly A GP working full time for 30 yrs might expect to see one or two cases in his/her course of work European population based registers report consistent incidence rates ( 2-3 per 100 000 person-years ) of amyotrophic lateral sclerosis Incidence of spinal muscle atrophy varies across populations
why important-MND is incurable but treatments that modify the disease and support services are available – can improve QOL and life expectancy Median survival is ~ 30 months but can vary with subtypes
Motor neurone disease- red flag diagnosis tool Painless , progressive weakness – could this be motor neurone disease ? 1 does the patient have one or more of these symptoms
Bulbar features –Dysarthria • Slurred speech often when tired Dysphagia • Liquids and / or solids • Excessive saliva • Choking sensation especially when lying flat Tongue fasciculations
Limb features – Focal weakness Falls / trips – from foot drop Loss of dexterity Muscle wasting Muscle twitching / fasciculations Cramps No sensory features
Respiratory features – Hard to explain respiratory symptoms Shortness of breath on exertion Excessive day time sleepiness Fatigue Early morning headache Orthopnoea
behavioural changes –Behavioral change Emotional lability ( not related to dementia ) Fronto- temporal dementia
2 is there progression- supporting factors- Asymmetrical features Age- MND can present at any age Positive family history of MND or other neurodegenerative disease
Factors not supportive of MND diagnosis- Bladder / bowel involvement Prominent sensory symptoms Double vision / Ptosis Improving symptoms
If yes to 1 and 2 query MND and refer to Neurology-If you think it might be MND please state explicitly in the referral letter. Common causes of delay are initial referral to ENT or Orthopaedic services
Bulbar features- 25 % of patients present with bulbar symptoms Dysarthria • Quiet , hoarse or altered speech • Slurring of speech often when tired Dysphagia – more often liquids first and later solids. Initially can be sensation of catching up in throat or choking when drinking quickly Excessive saliva Choking sensation when lying flat Weak cough – often noticed by the patient Painless progressive dysarthria – consider neurological referral rather than ENT
Limn features- 70 % of patients present with limb symptoms Focal weakness – painless with preserved sensation Distal weakness • Falls / trips – from foot drop • Loss of dexterity eg problems with zips or buttons Muscle wasting – hands and shoulders Typically asymmetrical Muscle twitching / fasciculations Cramps
respiratory features- Respiratory problems are often late feature of MND and an unusual presenting feature. Patients present with features of neuromuscular respiratory failure Shortness of breath on exertion Excessive daytime sleepiness Fatigue Early morning headache. Patients often describe a ‘ muzziness ‘ in the morning , being slow to get going or as if hung over Un-refreshing sleep Orthopnoea Frequent unexplained chest infections Weak cough and sniff Nocturnal restlessness and / or sweating Consider MND if investigations for breathlessness do not support a pulmonary or cardiac cause
Cognitive features- Frank dementia at presentation is rare. Cognitive dysfunction is increasingly recognised , as evidenced by : Behavioural change such as apathy or lack of motivation Difficulty with complex tasks Lack of concentration Emotional lability ( not related to dementia ) Ask specifically about a family history of these features.
Red flag diagnosis tool has been reproduced by kind permission of the Motor Neurone Disease Association www.mndassociation.org The tool has been developed by MND Association in collaboration with RCGP. The development group was made up of RCGP ( L Davies , R Pizarro-Duhart , I Rafi ) MND Association ( J Bedford , H Fairfield ) Neurology ( P Gallgher, C McDermott, K Morrison , R Orrell , A Radunovic , S Weatherby , A Wills ) Palliative Medicine ( I Baker )
NICE has produced guidance on MND – assessment and management February 2016 updated in July 2019 available at https://www.nice.org.uk/guidance/ng42
References
- Global burden of motor neurone diseases : mind the gaps The Lancet.com /neurology Vol 17 December 2018 https://www.thelancet.com/pdfs/journals/laneur/PIIS1474-4422(18)30398-3.pdf
- Motor neurone disease
- Motor Nuerone disease association – red flag diagnosis tool www.mndassociation.org
- Pathology of Motor Neurone Disorders emedicine.medscape.com
- ICD diagnosis code accessed via https://www.icd10data.com/ICD10CM/Codes/G00-G99/G10-G14/G12-/G12