Hypotonia

Clinic

• Hypotonia is an entity.
• ]Hypotonia is a state of low muscle tone, often involving reduced muscle strength.
• Hypotonia is a lack of resistance to passive movement, whereas muscle weakness results in impaired active movement.
• Central hypotonia (60 to 80%) originates from the central nervous system, while peripheral hypotonia is related to problems within the spinal cord, peripheral nerves and/or skeletal muscles.
• Severe hypotonia in infancy is commonly known as floppy baby syndrome.
• Hypotonia is thought to be associated with the disruption of afferent input from stretch receptors and/or lack of the cerebellum’s facilitatory efferent influence on the fusimotor system, the system that innervates intrafusal muscle fibers thereby controlling muscle spindle sensitivity. On examination a diminished resistance to passive movement will be noted and muscles may feel abnormally soft and limp on palpation. Diminished deep tendon reflexes also may be noted

Flaccid paralysis vs Hypotonia

Flaccid paralysis = Weakness / Paralysis + Hypotonia

Motor deficits

• Motor skills such assisting position, remaining seated without falling over, balancing, crawling, and sometimes walking
• Fine motor skills delays occur in grasping a toy or finger, transferring a small object from hand to hand, pointing out objects, following movement with the eyes, and self-feeding.
• Speech difficulties can result from hypotonia.

Muscle tone vs. muscle strength

• The low muscle tone associated with hypotonia must not be confused with low muscle strength
• Neurologic muscle tone is a manifestation of periodic action potentials from motor neurons. As it is an intrinsic property of the nervous system, it cannot be changed through voluntary control, exercise, or diet.
• True muscle tone is the inherent ability of the muscle to respond to a stretch.
• The child with low tone has muscles that are slow to initiate a muscle contraction, contract very slowly in response to a stimulus, and cannot maintain a contraction for as long as his 'normal' peers. Because these low-toned muscles do not fully contract before they again relax

Cause

• The most common cause of central hypotonia in newborns is hypoxic ischemic encephalopathy.
• There are many other causes which classified as Genetic, Developmental and Acquired.
• Infections causes are
  • Encephalitis
  • Guillain–Barré syndrome
  • Infant botulism
  • Meningitis
  • PLV

• Autoimmunity causes are
  • Myasthenia gravis (most common)
  • Celiac disease

• A rare but important cause is Sandifer syndrome