As you may already know, cerebral palsy refers to a family of related neurological disorders that affect muscle function, movement, balance and posture in around 17 million people worldwide. In two previous articles, we discussed the most common forms of the disorder, spastic and athetoid (or dyskinetic) cerebral palsy. Now, we’ll turn our attention to a comparatively-rare type of this condition: ataxic cerebral palsy.
The Cerebellum: Coordinating Movement & Balance
While all cases of cerebral palsy result from some form of brain damage or malformation, ataxic cerebral palsy has been linked to a specific brain structure, the cerebellum.
Sitting at the base of the skull, directly behind the brain stem and below the two cerebral hemispheres, the cerebellum plays an active role in motor control, taking crude electrical signals from the brain and spinal cord and tuning them to precision. The cerebellum makes fine motor functions and balance possible.
Damage to the cerebellum impedes this process.
One of the cerebellum’s primary functions is to coordinate disparate nerve signals and translate them into harmonized movements. As a result, injuries to the brain structure, often diagnosed as ataxic cerebral palsy, lead to problems in coordination.
Ataxia, a Greek word for “without order,” is an apt description. A patient’s movements will often appear clumsy or unstable. Usually, these symptoms manifest most intensely when a person tries to perform voluntary movements, which require precise muscle control. The technical term for this symptom is “intention tremor.”
When someone with ataxic cerebral palsy attempts to perform a controlled action, like writing with a pen, their affected limb can begin to tremble. This tremor becomes more pronounced as the movement progresses, ultimately making the desired action difficult to complete.
Impact On Muscle Tone
Ataxic forms of cerebral palsy can also affect a patient’s muscle tone. Muscle tone doesn’t refer to strength. It’s a technical scientific term to describe the amount of tension that muscles maintain in their resting state.
In people without cerebral palsy, muscles are never completely relaxed. Instead, they stay at the ready to perform reflexive actions and maintain a chosen posture at all times. People with ataxic cerebral palsy usually have abnormally-low levels of muscle tone.
This condition, known as hypotonia, makes maintaining a given body posture hard. In practice, hypotonia can make patients seem unsteady on their feet, as their body continually attempts to counterbalance changes in posture. To compensate, many children quickly develop a “wide-base gait,” spreading their feet far apart as they walk.
Damage to the cerebellum also makes it difficult for a patient’s body to compensate for changes in body posture. Ataxia makes walking an especially treacherous proposition. People with ataxic cerebral palsy, who often struggle to maintain balance, can fall easily. Slight nudges or changes in a walking surface can also lead to a fall.
These coordination problems generally affect the legs, arms and trunk, but they can also have an impact on muscles in the eyes and throat. A patient’s eye movement can seem slow, lagging behind changes in the visual environment. When a person with ataxic cerebral palsy tries to switch their attention, their eyes can overshoot the target. Speaking and swallowing can be difficult as well.
Some children born with cerebral palsy will also be affected by cognitive impairments. While many patients will grow to become exceptionally intelligent, other kids will develop cognitive delays or learning disabilities.
How Is Ataxic Cerebral Palsy Diagnosed?
Even after a child’s birth, brain development takes time. Most infants develop a full range of motor skills over the first two years of their lives. As a result, the effects of brain damage to the cerebellum often become apparent only after a child has begun to grow and learn through interaction with the world. Many kids with ataxic cerebral palsy will be diagnosed after parents notice that their child has failed to reach a developmental milestone, like crawling or taking a first step.
Early diagnosis is not impossible. After birth, lots of children who will eventually be diagnosed with ataxic cerebral palsy display marked symptoms of hypotonia, the low muscle tone we discussed earlier. During the first month of life, children may seem unusually sluggish, staying more immobile than other kids. Their limbs may appear weak or floppy and voluntary movements can seem uncoordinated. Impaired reflex responses can also serve as an early clue:
- Moro reflex – infants react to the feeling of falling in a characteristic way, by spreading and unspreading their arms and crying. Children with ataxic cerebral palsy will display this reflex for longer
Diagnostic imaging can be helpful to support a diagnosis, but haven’t yet replaced clinical exams in their accuracy. Neuro-imaging studies, like MRI, have been found to miss many children with cerebral palsy. A 2006 study in the journal Pediatrics, for example, found that MRI and CT scans failed to diagnose around one-third of children who had been previously-diagnosed with a cerebral palsy condition.
Like most children born with cerebral palsy, kids with ataxic forms of the disorder usually benefit from physical and occupational therapies. Physical therapists can help children develop physical strength and increase flexibility, while getting them used to orthotic devices, like walkers, that improve balance during walking. Occupational therapy, on the other hand, focuses on fine-motor skills and daily tasks, which can be particularly challenging for people with ataxic cerebral palsy.
Surgery is almost never considered for children with ataxic cerebral palsy.