Motor Neuron Disease (MND)

Exam Cram

• Motor Neuron Disease includes many subsets, ALS being the most common,

• Presentation: 60s with painless, progressive paralysis (PPP); with a mixed upper and lower motor neuron signs (without sensory changes)

• Diagnosis: clinical- EMG most useful investigation showing nerve de-innervation

• Management: Riluzole, MDT approach 

Outline

Background

• In Motor neuron disease (MND) the anterior horn cell is primarily affected- the cell in the spinal cord where the lower motor neuron (LMN) meets the upper motor neuron (UMN), 10% of cases are caused by genetic mutations

• Motor neuron disease has been made famous by the ALS Ice Bucket challenge and Stephen Hawkings, ALS being the most common subtype of MND

• The prognosis on diagnosis for ALS is on average 3 years, worse with respiratory or bulbar symptoms

Assessment

History

• Classically presents unilateral with e.g. foot drop, that persists and progresses

• Features of weakness: reduced exercise tolerance, dropping objects, 

• Respiratory/ bulbar signs (severe): short of breath lying flat at night, reduced cough/ speech

• Age 20-70yrs

Examination

• Muscle weakness

  • UMN: hypertonia, hyper-reflexia- jaw reflex, 

  • LMN: weakness, hypotonia, hyporeflexia, fasiculations, muscle wasting

  • Respiratory or bulbar signs: reduced cough, speech volume, breath count < 12

Investigations

• Electromyography- fibrillation and fasciculations

• Nerve conduction studies- normal (motor & sensation)

Diagnosis

Diagnosis: clinical

Differentials:  bilateral Mixed UMN + LMN lesions presentation-

• • • Subacute degneration of spinal cord- B12 deficiency- dorsal column affected (vibration/ temperature)

    • Syphilis - tabes dorsalis & SLE have broad presentations

    • Myelopathy- LMN at level, UMN below- no signs in cranial nerves (swallow, speech, jaw reflex negative)

• May have broad presentation: UMN, LMN or broad weakness only

Severity: respiratory or bulbar symptoms

Management

Long term

• Riluzole- adds 3 months to life expectancy so counselling is required and may not improve QoL

• MDT (see disease cycle below)

Disease Cycle

New Diagnosis

• History & examination

  • Severity- breath count < 12 ?NIV in HDU

  • Bulbar signs- cough, speech, swallow

• Investigations

  • Baseline- FBC, U&Es, CRP, LFTs + ECG

  • Neuro screen: B12, folate, blood sugar, HIV, Lyme Disease, Syphilis, ANA + anti-dsDNA (SLE)

  • Nerve Conduction Studies 

  • EMG

  • Likely MRI-H & Cervical Spine +- CT-H

  • Lumbar puncture if diagnostic uncertainty

• Management

  • Neurology Review

    • ? Diagnosis, ?Riluzole

    • Neurology OP Clinic FU

  • MDT Input

Post Diagnosis 

MDT

• Consultant Neurologist- specialty in MND

  • • Neurology Clinic FU

    • Riluzole discussion ?treatment goals

• Physio- exercises to maintain strenght

• OT- adapt home & work to ensure function, e.g. stair lift

• Nutrition & SLT- review swallow and nutrition for early long term RIG

• Respiratory: early morning ABG ?home NIV [early discussions]

• Genetic counselling & testing offered 

• Anticipatory- DNR discussions (not for ICU) +- palliative care/ End of Life

  • Symptoms: secretions

Subtypes

ALS: amyotrophic lateral sclerosis

• Commonest type of motor neuron disease

• Presentation: LMN weakness upper limbs

• Pathology: anterior horn cells

References and Resources

Links

• Body systems: Nervous system

• Specialties: Neurology (also Respiratory,  Gastroenterology & Palliative Care)

References

1. Arora RD, Khan YS. Motor Neuron Disease. [Updated 2023 Aug 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK560774/

Page written in 2024, updated 2026.