NEUROMUSCULAR DISORDERS

In this blog I will try to describe some facts about neuromuscular disorders in brief so that the readers can get an overview of the problems and some of the key points they should keep in mind during a clinical assessment.

All these disorders are classified under LOWER MOTOR NEURON DISEASES. To make it simpler we can classify them into five broad categories; like diseases due to involvement of :

  • ANTERIOR HORN CELLS
  • ANTERIOR ROOT (which is the efferent root of a spinal nerve)
  • PERIPHERAL NERVES
  • NEUROMUSCULAR JUNCTIONS
  • MUSCLES.

Now there is a basic inter group difference between diseases involving ANTERIOR ROOTS and PERIPHERAL NERVES combined together and the rest of the three categories and that is SENSORY INVOLVEMENT. These disorders show weakness along with sensory issues.

When we want to distinguish between RADICULOPATHY AND NEUROPATHY these points will help to simplify the clinical diagnosis:

  • Neuropathies always have a symmetrical presentation.
  • Distal components (hands, toes) are involved along with hypersensitivity.
  • On the other hand Radiculopathies are asymmetrical.
  • Involve proximal components and are accompanied by pain.

 

Differences between disorders involving anterior horn cells and the muscles :

A] ANTERIOR HORN CELLS :

The anterior horn is the ventral horn of grey matter section in  the spinal cord. The anterior horn contains motor neurons that affect the axial muscles and here is where the cell bodies of alpha motor neurons are located.

It is these cells that are affected in the “anterior horn diseases“, namely amyotrophic lateral sclerosis, Charcot–Marie–Tooth disease, progressive muscular atrophy, poliomyelitis etc. In these diseases we can see distal as well as proximal components getting involved. Wasting of muscles is prominently seen. These are always asymmetrical. Hypertrophy is present but not as much as seen in muscular dystrophies. Hallmark of AHC disease is fasciculations. Deep tendon reflexes are absent.

B] MUSCLES :

In diseases involving muscles like for e.g. DUCHENNE’S MUSCULAR DYSTROPHY weakness is majorly proximal. Hypertrophy is very prominent. Wasting can be seen but in late stages of disease. Fasciculations are absent and deep tendon reflexes are maintained for long time.

Now coming to disorders in which neuromuscular junctions are involved. Most common known disease is MYASTHENIA GRAVIS.

A patient with Myasthenia Gravis will have a chief complaint of FATIGUE. The basic difference between weakness and fatigue is that a person with weakness will experience it throughout the day whereas fatigue arises after repetitive activities towards the end of the day. There is diurnal fluctuation. Myasthenia gravis affects particular muscle groups mainly present above the neck region. Persons with MG have diplopia, ptosis and difficulty while chewing food, breathing and swallowing.

In the end I hope, through this blog I could clear some basic concepts regarding the NEUROMUSCULAR DISORDERS.