Hypotonia or lack of muscle tone is a sign of an underlying disease or condition. It may be seen at birth or may be acquired later in life. The aim of diagnosis is to detect the cause of the condition.
If hypotonia is detected in a newborn baby or child by a paediatrician, a referral to a neurologist of a specialist is made.
Who diagnoses hypotonia?
Management of hypotonia involves a multidisciplinary team. This includes an occupational therapist, physiotherapist, speech and language therapists an orthopaedic surgeon etc.
History of pregnancy
Diagnosis begins with detailed history: the mother is asked about her pregnancy and delivery.
She will be asked if any family member had a similar problem or if the baby suffered seizures after birth.
During pregnancy low fetal movements, breech presentation (this is the opposite of the normal head-down position of a baby inside the womb), increased or decreased amniotic fluid (polyhydramnios or oligohydramnios) etc. are relevant findings.
History of trauma at birth, premature delivery, late cry of the baby after birth, abnormal pH of the fetal umbilical cord blood etc. are also relevant findings.
Full physical examination
This is followed by a full physical examination. Some conditions can be detected with an initial physical examination.
For example, congenital genetic disorders like Down’s syndrome or congenital conditions like cerebral palsy may be detected with thorough clinical examination.
A frog like position, a “lag” or falling back of the head when the baby is pulled up to sitting position by the hands, weakness of the trunk and other muscles, laxity or over-flexibility of the joints are diagnostic clinical findings of hypotonia.
Tests for hypotonia
There are several tests and imaging studies advised for hypotonia, these include blood tests, assessment of cerebrospinal fluid and so forth. (1-4)
These can detect any routine abnormality. Blood biochemistry can show disturbance of any minerals or vitamins in blood.
Assessment of thyroid hormone in the blood can help detect hypothyroidism that may have caused the symptoms of hypotonia.
A complete blood count reveals if there is an infection in the body.
Sepsis (generalized infection) or infection of the brain or meninges (encephalitis or meningitis) may be suspected using routine blood tests.
Blood tests like metabolic panel tests are a series of blood tests may be prescribed to check whether the body’s metabolism is working properly. This can diagnose storage diseases.
Creatinine kinase levels may be disturbed in certain muscle disorders. Blood tests for creatinine kinase may be prescribed.
Assessment of Cerebrospinal fluid
Assessment of Cerebrospinal fluid (CSF) by lumbar puncture may be used to detect meningitis or encephalitis.
The CSF usually circulates throughout the brain and spinal cord. Any infection of the brain or its parts is detected using a microscopic examination of the CSF.
A muscle biopsy may be prescribed in some patients. A small sample of muscle tissue is cut out from the muscle and sent to the pathologist who examines in under the microscope.
Sometimes electron microscopic picture of the muscle sample may be tested.
Other tests for hypotonia
Other tests for hypotonia include:
- Computerized tomography or CT scan or Magnetic Resonance Imaging (MRI) scan to find out if there are any abnormalities or damage in the central nervous system
- EEG (Electroencephalogram) – test to detect the electrical brain waves and brain activity
- Electromyography (EMG) - Electrical activity of a muscle is recorded using needle like electrodes which are inserted into the muscle fibres
- Nerve conduction velocity – The speech of conduction of an impulse via a nerve is measured using small metal disc electrodes placed over the skin over the nerve
- Genetic testing may be recommended for parents and the affected child when an inherited disorder like Down’s syndrome etc. is suspected.
- If no abnormalities are found the patient is termed to be suffering from benign congenital hypotonia.
Edited by April Cashin-Garbut, BA Hons (Cantab)
What is hypotonia?