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Motor Neurone Disease

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Motor Neurone Disease

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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 )

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 Motor neurone disease BMJ 2014 ; 349 :g4052 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

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