Alternating Hemiplegia

Definition

Definition of Alternating Hemiplegia
Alternating hemiplegia refers to a form of hemiplegia that has an ipsilateral and contralateral presentation in different parts of the body. The disorder is characterized by recurrent episodes of paralysis on one side of the body. This type of syndrome can result from a unilateral lesion in the brainstem affecting both upper motor neurons and lower motor neurons. The muscles that would receive signals from these damaged upper motor neurons result in spastic paralysis. With a lesion in the brainstem, this affects the majority of limb and trunk muscles on the contralateral side due to the upper motor neurons decussation after the brainstem. The cranial nerves and cranial nerve nuclei are also located in the brainstem making them susceptible to damage from a brainstem lesion. Cranial nerves III (Oculomotor), VI (Abducens), and XII (Hypoglossal) are most often associated with this syndrome given their close proximity with the pyramidal tract, the location which upper motor neurons are in on their way to the spinal cord. Damages to these structures produce the ipsilateral presentation of paralysis or palsy due to the lack of cranial nerve decussation (aside from the trochlear nerve) before innervating their target muscles. The paralysis may be brief or it may last for several days, many times the episodes will resolve after sleep.

Symptoms

Symptoms of Alternating Hemiplegia
Some common symptoms of alternating hemiplegia are mental impairment, gait and balance difficulties, excessive sweating and changes in body temperature.

Causes

Causes of Alternating Hemiplegia
We do not know what causes alternating hemiplegia to develop but we do know that it is a very rare condition, affecting about one in every million children. Symptoms usually appear before a child is four years old and then come and go over time.

Diagnosis

Diagnosis of Alternating Hemiplegia
The main problem with diagnosis is that the condition is extremely rare and symptoms come and go over time. As a result, the condition may be misdiagnosed in the early stages.

There is no specific diagnostic test and doctors tend to diagnose it by looking at a child’s history and symptoms. In many children, diagnosis takes a long time and may have involved many different specialist doctors. Once a diagnosis has been made, a multidisciplinary team, including both specialist and local doctors, are best placed to manage affected children.

Treatment

Treatment of Alternating Hemiplegia
A drug called flunarizine, which is a calcium channel blocker can help to reduce the severity and the length of attacks of the paralysis.

Prognosis

Prognosis of Alternating Hemiplegia
The variation in function in between and during episodes needs to be understood by all involved with the child. For example, a child may be able to walk reasonably well for some of the time, but need a wheelchair or buggy sometimes, often with little warning.

While it is not a progressive disease, it seems that episodes of weakness may get worse over time and recovery may become slower.

Prevention

Prevention of Alternating Hemiplegia
In about half of children, there seems to be a ‘trigger’ for episodes of weakness. These vary from child to child and include exposure to cold, emotional stress, tiredness, bathing, high temperatures and respiratory infections. While avoiding these triggers may reduce the risk of an episode, it can also have a negative effect on family life, so a balance between prevention and normality needs to be reached after discussion with the team.

Anti-seizure medicines have been used in the past to prevent episodes but these do not work very well. Other medicines have also been tried, for instance, antimigraine medicines, but these are not used very often. Flunarizine, a calcium channel blocker, has been used widely, although it rarely stops episodes completely. However, it does seem to reduce the severity of episodes and how long they last. Some parents also reported that episodes happen less often.