Abnormally increased muscle tone is called hypertonia, which may cause muscle stiffness and difficulty in moving the limbs. Hypertonia is less common among babies than hypotonia (floppy baby syndrome).
The condition is a central nervous system pathology and could be present at birth or develop after birth. Some babies may have transient hypertonia that resolves in a short time, while a few may have persistent hypertonia that may stay for a lifetime.
Read this post to learn about causes, risk factors, signs, treatment, and hypertonia outcomes in babies.
Causes Of Hypertonia In Babies
Muscle tone is a muscle’s resistance to stretch. The muscle tone is regulated by the central nervous system (the brain, spinal cord, and nerves) through nerve signals that contract and relax the muscle. In hypertonia, the nerve pathways that control the muscle are disrupted due to damage to the central nervous system (CNS).
The following conditions and factors may lead to CNS damage (1).
- Brain tumors
- Head injuries
- Neurodevelopmental anomalies, such as cerebral palsy
- Neurodegenerative diseases
Babies who develop hypertonia after a fall or blow to the head should be taken to emergency care. Some of these conditions may also cause hypotonia (low muscle tone) or floppy baby syndrome. Consult a doctor to determine the precise underlying cause.
Signs And Symptoms Of Hypertonia
Hypertonia signs and symptoms may vary depending on the severity of the damage and the part of the brain or spinal cord affected. Some babies may have high muscle tone on both sides of the body, while a few may have it on one side.
Common signs and symptoms seen in hypertonia in babies include the following (2).
- Reduced range of motion
- Stiff or rigid muscles
- Body deformity
- Awkward muscle contractions
- Frozen or fixed joints
- Unable to walk or stand as peers
- Involuntarily crossing of the legs
According to the affected area of the brain, hypertonia can be spastic or rigid. Spasticity causes higher reflex responses and increased muscle spasms. Rigidity causes excessive stiffness of the muscles.
Diagnosis Of Hypertonia
History of symptoms and physical examination can be enough to identify the presence of hypertonia in babies. Additional tests, such as blood test, CSF analysis, and imaging tests (MRI scans), are ordered to look for brain anomalies (1).
Blood tests and CSF analysis help identify infections and determine neurotransmitter levels. Specific tumor markers and toxins can also be determined from blood tests. Neuroimaging helps visualize structural anomalies and intracranial hemorrhages that often occur after head injuries.
Treatment For Hypertonia In Babies
- Baclofen, a muscle relaxer and an antispasmodic drug, is prescribed as a first-line treatment for babies with brain anomalies.
- Benzodiazepines, such as diazepam, are also used in initial treatment for hypertonia due to brain problems.
- Vitamins are often prescribed for babies with seizures.
- Levodopa, a type of amino acid, is given to babies with CNS-related causes but with no abnormalities seen in neuroimaging tests.
- Carbamazepine and phenytoin are prescribed for peripheral nervous system-related causes of hypertonia.
- Botox (botulinum toxin) injections could be given to relax hypertonic muscles.
- Physiotherapy could be conducted, often in conjunction with other treatments, to improve muscle tone.
If hypertonia is a result of another condition, it could also be treated simultaneously.
Prognosis Of Hypertonia In Babies
The outcome may vary based on the severity of hypertonia and the underlying cause. Hypertonia with cerebral palsy may often stay without change over a lifetime. In some cases, the hypertonia may worsen as the underlying condition worsens over time (4).
Mild hypertonia may cause no effect as the baby grows older. In contrast, moderate hypertonia may increase the risk of abnormal joint contractions, which increase the risk of falls. Severe hypertonia could increase the risk of several complications, such as fractures, bedsores, infections, and severe immobility.
Hypertonia could limit the child’s range of motion and physical abilities. Thankfully, prolonged occupational and physical therapy could improve muscle tone. Several assistive devices, such as special wheelchairs, can make limitations manageable. Parental support and continuous therapy could improve the child’s quality of life and enable them to perform tasks like their peers.
2. Hypertonia; Physio UK
3. Hypertonia; Intermountain Healthcare
4. Hypertonia; Child Neurology Foundation