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n_mnd

motor neurone disease (MND)

Introduction

  • a group of progressive neuronal degenerative diseases with generally poor prognosis
  • when one talks on MND, they are usually referring to ALS which is a type of motor neuron disease

Patterns of weakness

  • Asymmetric distal weakness without sensory loss
    • ALS, PLS, PMA, MMA
  • Symmetric weakness without sensory loss
    • PMA, PLS
  • Symmetric focal midline proximal weakness (neck, trunk, bulbar involvement)
    • ALS, PBP, PLS

Amyotrophic lateral sclerosis (ALS)

  • aka Lou Gehrig's disease
  • progressive degeneration of motor nerve cells in the brain (upper motor neurons) and spinal cord (lower motor neurons)
  • most develop it between 40-70yrs, especially 60-70yrs but can occur younger
  • similar incidence as multiple sclerosis (MS) and accounts for 5 of every 100,000 adult deaths
  • no cause found in 90% of cases, 5% have a clear AD genetic cause with:
    • 25-40% of the familial form of ALS in adults is caused by a defect in a gene known as “chromosome 9 open reading frame 72,” or C9ORF72
    • 10-12% of the familial cases having mutations in the gene for the enzymes superoxide dismutase 1 (SOD1) or copper zinc superoxide dismutase
  • there is a suggestion that dietary exposure to a blue-green algae toxin known as β-N-methylamino-L-alanine (BMAA) may be causative and that a diet of L-serine may partly prevent it, at least in animal models 1)

Classification of ALS

Classical ALS

  • 2/3rds of cases of ALS
  • “people first experience awkwardness when walking or running or even tripping over or stumbling may be experienced and often this is marked by walking with a “dropped foot” which drags gently on the ground. Or if arm-onset, difficulty with tasks requiring manual dexterity such as buttoning a shirt, writing, or turning a key in a lock may be experienced”

Progressive Bulbar Palsy (PBP)

Progressive Muscular Atrophy (PMA)

  • rare, mainly affects LMN neurones

Familial

  • 5-10% of cases of ALS

Primary Lateral Sclerosis (PLS)

  • rarest form of ALS; mainly affects UMNs

Diagnosis of ALS

  • Body segments for the diagnostic criteria are: bulbar, cervical, thoracic and lumbar myotomal regions
  • Lower motor neuron (LMN) findings include muscle atrophy and fasciculations
  • Upper motor neuron (UMN) findings include hyperreflexia, spasticity, and muscle spasm
  • bulbar (LMN) features are:
    • difficulty speaking (dysarthria), difficulty swallowing (dysphagia), and excessive saliva production (sialorrhea)
    • wasted tongue with fasciculations
    • absent gag reflex
    • nasal speech
  • pseudobulbar (UMN) features are:
    • labile emotion with pseudobulbar affect, problems in word fluency, decision-making, and memory
    • small, tight, spastic tongue which cannot be protruded and lies on the floor of the mouth
    • monotonous, slurred, high-pitched, ‘Donald Duck’ dysarthria”
    • increased jaw jerk

World Federation of Neurology (WFN)

  • clinically definite:
    • UMN and LMN signs in at least 3 body segments
  • clinically probable:
    • UMN and LMN signs in at least 2 body segments with some UMN signs in a segment above the LMN signs
  • Clinically probable, laboratory-supported ALS:
    • UMN and LMN signs in 1 segment or UMN signs in 1 region coupled with LMN signs by electromyography (EMG) in at least 2 limbs
  • Clinically possible ALS:
    • UMN and LMN signs in 1 body segment, UMN signs alone in at least 2 segments, or LMN signs in segments above UMN signs
  • Clinically suspected ALS:
    • Pure LMN syndrome with other causes of LMN disease adequately excluded
n_mnd.txt · Last modified: 2020/05/21 18:58 by gary1