Symptoms of hypotonia

By Dr Ananya Mandal, MD

Hypotonia is a condition where there is decreased resting muscle tone. It is a symptom of an underlying condition that may be congenital (present since birth) or acquired (manifested later in life).

General symptoms of congenital hypotonia

Congenital hypotonia usually manifests as (1-4):

• Muscle weakness that is noticeable by the time the baby is six months old
• Initial symptom is a weak cry and inability to suck or swallow
• Little or no control of neck muscles leading to a floppy head and lack of head-holding
• Feeling of a limp body when held
• Inability to place any weight on legs or shoulders
• The baby’s arms and legs hang straight down from sides, rather than bending at the elbows, hips and knees.
• Delayed achievement of motor growth developmental milestones like sitting up, crawling, walking, talking or feeding themselves
• Frequent falls and slipping off the high chair
• If there are severe congenital myopathies there may be accompanying skeletal or bone and joint abnormalities. These include propensity for hip dislocation, deformities of the spine and foot.
• On examination of a hypotonic child there is weakness of the muscles of the face, trunk or foot and ankle muscles.

  There may be ptosis or drooping eyelids, wing like outward protrusion of the scapula bones of the back and a thin body.

  There may be a protrusion of the abdomen due to weak abdominal muscles that are unable to hold in the contents of the abdomen.

• Most patients with hypotonia may develop insufficiency of breathing and 50% of patients between ages 3 and 55 years need some form of artificial method to help them breathe at night.

Symptoms of congenital hypotonia that relate underlying conditions

• Symptoms of mental retardation in cases of underlying conditions like Down’s syndrome
• In Down’s syndrome, additional features include mental retardation, and congenital heart defects. There may be abnormal facial features like flat nose and nasal bridge, short neck, single transverse crease over the palm, upwardly slanting eyes etc.
• In children with Fragile X syndrome there may be hypotonia along with features like mental retardation, large head (macrocephaly), large ears, and large testicles at puberty, autism like features etc.
• Prader Willi syndrome is manifested as hypotonia, small genitals, short height and obesity.
• Myasthenia gravis – If the baby develops transient or short term myasthenia due to an affected mother there may be symptoms like sepsis that include poor cry, poor suckling, hypotonia etc.

  In case of a baby affected primarily with myasthenia gravis the symptoms are exaggerated. There may be ptosis or drooping of the eyelids and respiratory or breathing difficulties.

Symptoms of acquired hypotonia

In case of acquired hypotonia or adults with hypotonia the usual manifestations include (3-4):

• Clumsy behavior that progressively worsens
• Frequent falls
• Inability or difficulty getting up from a lying or sitting position
• Difficulty in reaching for or lifting an object
• High flexibility of joints called joint laxity. This may occur at hips, elbows and knees

Specific symptoms of hypotonia

Specific symptoms and signs of hypotonia include (2) –

1. Central hypotonia – This is seen in 60-80% cases. There may be additional problems like seizures, inability to track a visual object, failure to imitate facial gestures, lethargy etc.
2. Peripheral Hypotonia – Seen in 15-30% of cases. These patients manifest with feeding difficulties, generalized weakness and absence of muscle reflexes on testing.

Edited by April Cashin-Garbutt, BA Hons (Cantab)

Further Reading

What is hypotonia?
Hypotonia Causes
Hypotonia Diagnosis
Hypotonia Treatments

Sources:

1. http://emedicine.medscape.com/article/1175852-clinical
2. http://pedclerk.bsd.uchicago.edu/hypotonia.html
3. http://www.nhs.uk/Conditions/hypotonia/Pages/Symptoms.aspx
4. http://www.knowsley.nhs.uk/health-a-to-z/h/hypotonia/