What is Hypertonia (and Hypotonia)?

What are Hypertonia and Hypotonia?

Child Trying to WalkHypertonia and hypotonia are two very similar words that have opposite meanings. Both words relate to problems with someone's muscle tone, with the term "tonia" literally meaning "muscle tension". When we use the muscles in our body, we are repeatedly stretching and contracting them as we move.

Think of a rubber band. When we stretch, the tension on our muscles increases. This is why we feel resistance. With hypertonia and hypotonia, the muscle tension is abnormal. Let's break down these conditions to understand how they affect people differently.

What is Hypertonia?

The term "hyper" means over, above, or excessive. Hypertonia is when someone has too much muscle tone in their body, making it hard to flex and move around normally. People with hypertonia will have issues with stiff movements, balance, walking and reaching. In some cases, someone can also have problems with feeding. There are two main types of hypertonia:

  • Spastic hypertonia: This type of hypertonia causes the body to have random and uncontrollable muscle spasms. The spasms can affect one or multiple muscle groups throughout the body. The primary cause of this type comes from injury to the spinal cord or brain, which is often associated with the condition of cerebral palsy.
  • Dystonic hypertonia: This type is associated with muscle rigidity and lack of flexibility. A person with dystonic hypertonia can have an involuntary posture due to their inability to stretch the muscles. Dystonic hypertonia is commonly associated with Parkinson's Disease.
What Causes Hypertonia in Babies?

The underlying cause of hypertonia is an injury to a baby's central nervous system. This injury can occur while developing in the womb, during the delivery process, or shortly after birth. A damaged central nervous system cannot communicate properly to the motor pathways, making the body unable to control its muscle tone and reflexes.

Hypertonia is closely associated with birth injuries, such as an injury to the head or lack of oxygen while traveling down the birth canal. This is also why hypertonia is often diagnosed along with cerebral palsy, another condition that develops due to brain damage from a birth injury. Hypertonia can also be caused by diseases like Parkinson's.

How is Hypertonia Treated?

Treatment for hypertonia usually consists of different types of muscle relaxant medications and continuous physical therapy. The three most popular medications used to treat the condition are Baclofen, Diazepam, and Dantrolene. Some patients use special injections to directly treat an affected muscle. The type of specific treatment for someone also depends on the underlying cause of their condition.

What is the Prognosis of Hypertonia?

The prognosis for this condition will depend on the cause and severity. If hypertonia is caused by cerebral palsy, the symptoms are known as non-progressive, meaning they will not worsen over time and they can often be managed with therapy and medication. If hypertonia is caused by a condition like Parkinson's, the symptoms can increase as the disease progresses.

Mild hypertonia may not cause any significant issues in life. Moderate hypertonia may get worse from falls or joint contractures, which can impact a person's health. Severe hypertonia may cause permanent mobility problems and increased bone fragility. People with severe hypertonia might have to stay in one position for long periods of time, which puts them at risk of bedsores and pneumonia.

What is Hypotonia?

Now that you know "hyper" means excessive, it only makes sense that "hypo" means under or less. Hypotonia causes decreased muscle tone and increased flexibility, making the body seem floppy or limp. Hypertonia is also known as "floppy infant syndrome".

A child with hypotonia will have problems lifting their limbs and performing fine and gross motor activities. This means they may have trouble sitting up with no support, feeding themselves, and using coordinated and controlled movements. The joints will feel extremely flexible, like how some people are double-jointed.

What Causes Hypotonia in Babies?

The underlying cause for hypotonia is the same as hypertonia in the sense that there is abnormal neurological control of muscle tone. Just like hypertonia, this neurological damage is often caused by birth injuries, but can also stem from serious infections, such as meningitis. Head and spinal cord injuries are the most common injuries that occur when someone develops this condition. Cerebral palsy is still closely associated with hypotonia, and the two diagnoses often go together. Other neurological problems that can cause hypotonia include

How is Hypotonia Treated?

Treatment for hypotonia will depend on the cause of the condition. Like we mentioned above, hypotonia stemming from cerebral palsy is non-progressive. Other neurological conditions may improve or get worse over time. In general, however, treatment is focused on improving and supporting muscle function. Common treatments include physiotherapy, occupational therapy, and speech therapy. Moderate to severe cases of hypotonia may require a person to use special equipment to help them stay mobile.

What is the Prognosis for Hypotonia?

The prognosis of hypotonia will change depending on the cause of the condition, the type of impact it has on a person's life, and their overall health. Hypotonia can be a life-long condition for many people, but in some cases, a person's muscle tone can improve over time. Hypotonia caused by infection, prematurity, or myasthenia gravis has a better prognosis than other causes, such as cerebral palsy.

Can Hypertonia or Hypotonia be Prevented?

Currently, there is no way to prevent hypertonia from occurring, especially if it was caused by a birth injury. Hypotonia, however, may be able to be prevented through early diagnosing and treating underlying conditions, unless it developed from brain injury. Unfortunately, damage to the brain early in life can be extremely hard or impossible to correct, which is why both conditions are known for being permanent.

Outlook With Hypertonia and Hypertonia

The treatment and prognosis of the condition will be unique to each person depending on the underlying cause and how it impacts their life. Hypotonia may be able to improve with pharmacologics and therapy. But the underlying conditions are usually permanent.

Sources and Additional Literature
  • Dy, R., & Roge, D. (2019). Medical Updates in Management of Hypertonia. Physical Medicine and Rehabilitation Clinics, 31(1), 57-68 (a look at pharmacologic therapies in the treatment of hypertonia)
  • Mercuri, E., et al. (2019). Neonatal hypotonia and neuromuscular conditions. In Handbook of clinical neurology (Vol. 162, pp. 435-448). Elsevier (diagnosing hypotonia early to identify the need for early intervention).
  • Hart, A. R., et al. (2015). Neonatal hypertonia-a diagnostic challenge. Developmental Medicine & Child Neurology, 57(7), 600-610.
  • Sparks, S. E. (2015). Neonatal hypotonia. Clinics in perinatology, 42(2), 363-371.
  • Francisco GE, et. al: Consensus panel recommendations for the use of intrathecal baclofen therapy in post-stroke spastic hypertonia. Top Stroke Rehabil 2006; 13: 74-85.
  • Scher, M. S. (2008). Neonatal hypertonia: I. Classification and structural-functional correlates. Pediatric neurology, 39(5), 301-306 (baclofen decreases spasticity but also reduced excitability of neural structures underlying voluntary motor tasks)
  • Horn TS, et.al: Effect of intrathecal baclofen bolus injection on gait in persons with lower extremity spastic hypertonia due to acquired brain injury: temporo-spatial outcomes. Arch Phys Med Rehabil 2005; 86: 1127-33 (found that ITB bolus injection reduces spasticity but does not necessarily improve the patient's ability to walk)
  • Yablon SA, et al: Neurophysiologic evaluation of spastic hypertonia: Implications for management of the patient with the intrathecal baclofen pump. Am J Phys Med Rehabil 2004;83(Suppl):S10-18.