According to the terminology used in this website, ALS is classified as motor neuron diseases (MND). What does it mean? The motor neuron diseases are a group of a few diseases, all destroying the so called motor neurons. However, the symptoms, disease course and prognosis vary with each disease. The main disease in the group of MND is Amyotrophic Lateral Sclerosis, which constitutes the majority of MND cases. In practice, the symptoms of Motor neuron diseases overlap and that is why a disease classified as MND my transform into full-blown ALS after some time (Adamek, Tomik).

Table A. Conditions classified as Motor Neuron Diseases.
Motor Neuron Diseases
UMN- upper motor neuron
LMN- lower motor neuron
Amyotrophic lateral sclerosis (ALS) Signs of UMN and LMN damage
Progressive muscular atrophy (PMA) Signs of LMN damage only
Primary lateral sclerosis (PLS) Signs of UMN damage only
Progressive bulbar palsy (PBP) Signs of cortico-nuclear pathways, motoneuron nuclei and brain-stem nerves /V, VII, IX, XI, XII)

You can read about other diseases classified as motor neuron diseases (MND) in a book entitled "Stwardnienie zanikowe boczne". A medical knowledge on neurology in indispensable to fully understand the book.

Table B. Conditions classified as Motor neuron disorders.
Motor Neuron Diseases*
*modified and shortened version ( Lowe and Leigh, 2002)
primary secondary
sporadic motor neuron diseases familial motor neuron diseases
  • infection inflammatory diseases and motor-neuron damages (e.g. inflammation of the anterior horns of the spinal cord, post-polio syndrome, HIV infection, syphilis)
  • metabolic disorder (e.g. hyperparathyroidism)
  • disorders due to irradiation
  • disorders caused by exogenous factors (mainly lead)
  • disorders caused by immune reaction
    (e.g due to lymphoproliferative disorders)
  • neurodegenerations other than ALS, in which motor neuron damage can occur
    (e.g. Huntington's disease, prion diseases)
  • sporadic ALS
  • sporadic ALS-plus syndrome (with, e.g., dementia,)
  • ALS +parkinsonism +dementia (islands in the West Pacific)
  • familial ALS
  • Spinal Muscular Atrophy (SMA) (autosomal-recessive disorder)
  • Kennedy's syndrome
  • juvenile ALS
  • familial ALS with dementia

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Symptoms typical of PBP result from damages to motor nuclei and V, VII, IX, X, XI, XII cranial nerves of brain stem and cortico-nuclear pathways. PBP constitute nearly 25% of all MND cases. Mixed symptoms (bulbar- pseudobulbar) are located only at the bulb level. The syndrome (isolated even for a few years) can be an onset of full-blown ALS. Hence, the EMG examination is mainly performed to find symptoms of LMN- damage in extremities of PBP- patients. PMA is characterized by lower motor neuron damage only, what results in weakness and atrophy of the muscles of extremities (especially in hands), reduction or absence of deep reflex. Usually the damage symptoms do not occur at the bulb level (i.e. brain stem). In that rare form of MND the mean survival time is between 30 and 40 years (10% of all MND-cases). PLS is characterized by upper motor neuron damage. Most often, UMN involvement presents as gradually developing spastic paraparesis with exaggerated responses, Babinski's sign and spastic tone higher that paresis itself. Spastic tone is to blame for walking difficulties. Gradually developing spastic dysarthria rarely occurs in PLS patients. About 5% of MND patients develop PLS with slow and long-term regression (Strong & Gordon, 2005).

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