NeurometPlus

Incidence

Rasmussen’s syndrome is a rare, progressive neurological disorder. There is no major difference in incidence between sexes or prevalence in any population group. There are probably somewhere between 200 and 500 cases worldwide. In the U.S and Canada, since 1958, there have probably been around 200 cases diagnosed. Diagnosis is dependent on the degree of neurologic sophistication in the country or area where the patients live. In about 50% of patients, the onset is preceded by an inflammatory episode (eg, an upper respiratory tract infection, otitis media, or tonsillitis) occurring in the previous 6 months.

Clinical Characteristics

Rasmussen’s syndrome is a very rare form of brain malfunction that most commonly affects children aged 1 to 10 years of age. The cause is unknown, although occasionally a virus may be present initiating an immune response. Some cases are thought to follow viral infections, such as influenza and measles, or head injury. The brain cells in one hemisphere become swollen, and the inflammation causes the malfunction of the brain cells. This in return causes epilepsia partialis continua. It is considered an epileptic syndrome. The most commonly affected parts of the brain are the frontal lobe and the temporal lobes. Many of the seizures involve simple partial motor seizures causing rhythmical jerking of the arm and/or leg on the opposite side of the body. These seizures are often refractory to medications. The intractable seizures often lead to hemiparesis or hemiplegia. As the seizures continue, this weakness worsens. The EEG is abnormal from the beginning course of the condition, but the MRI may be normal, until months of years after the condition begins. The MRI shows evidence of brain atrophy in the affected part of the brain. Treatment options include lobectomy or in most cases, hemispherectomy of the affected brain. This surgery may cure the condition, yet it is rare. After several years of the inflammatory process, the condition seems to decelerate without further progression. However, the damage that was done is irreversible and the seizures continue to occur, though there is a better chance of seizure control. Over the course of the condition, hemiparesis and learning difficulties develop. This condition is rarely fatal.

Precipitants

None

Provocation Tests

None

Diagnostic Procedures

It is a clinical diagnosis. Negative standard viral studies (or positive reactions only to herpes simplex and measles virus in low dilution, which is of doubtful clinical significance). There has been some evidence tying this condition to GRIA3 (GluR3), but recent studies have been inconclusive. EEG is abnormal from the onset of the condition.