NORD gratefully acknowledges Gary W. Mathern, MD, Professor and Neurosurgical Director, Pediatric Epilepsy Surgery Program, Departments of Neurosurgery and Psychiatry & Biobehavioral Medicine, Mattel Children's Hospital, David Geffen School of Medicine, UCLA; William Davis Gaillard, MD, Professor, Pediatrics and Neurology, George Washington University School of Medicine, Professor Neurology, Georgetown University, Chief, Epilepsy, Neurophysiology, and Critical Care Neurology, Children's National Medical Center, Associate Director, Center for Neuroscience Research, Children's Research Institute; Prof. J. Helen Cross, The Prince of Wales's Chair of Childhood Epilepsy UCL-Institute of Child Health, Great Ormond Street Hospital for Children & Young Epilepsy and Head of Neurosciences Unit, UCL-Institute of Child Health, London, for assistance in the preparation of this report.
Rasmussen encephalitis, sometimes referred to as Rasmussen syndrome, is a rare disorder of the central nervous system characterized by chronic progressive inflammation (encephalitis) of one cerebral hemisphere. As a result, the patient usually experiences frequent episodes of uncontrolled electrical disturbances in the brain that cause epileptic seizures (epilepsy), and progressive cerebral destruction. With time, further symptoms may include progressive weakness of one side of the body (hemiparesis), language problems (if on the left side of the brain) and intellectual disabilities. The exact cause of this disorder is not known. The two leading ideas are that the brain inflammation might be a reaction of a foreign antigen (infection) or an autoimmune disease limited to one side of the brain resulting in brain damage. It occurs mostly, but not always, in children between the ages of two and ten years, and in many patients the course of the disease is most severe during the first 8 to 12 months. After the peak inflammatory response is reached, the progression of this disorder appears to slow or stop and the patient is left with permanent neurological deficits.
Typically, affected individuals develop focal seizures that may progress to near continuous seizures termed epilepsia partialis continua (EPC). EPC is characterized by a rapid, rhythmic succession of contractions and relaxations of a muscle or muscle group (myoclonus), particularly of the arms, legs, and face, that may occur singularly or in a repetitive, continuous series. In Rasmussen this occurs consistently on one side of the body opposite the side of the inflammation.
Most affected children will exhibit progressive paralysis of one side of the body (hemiparesis) and if the seizures continue developmental disabilities. In many cases, the development of physical and mental abilities of affected children may cease (developmental arrest). In addition, affected children may lose previously acquired physical and mental abilities (developmental regression). Some affected children may exhibit degeneration (atrophy) of one side of the brain and/or progressive confusion, disorientation, and deterioration of intellectual abilities (dementia).
The exact cause of Rasmussen encephalitis is not known. Most researchers now suspect that Rasmussen encephalitis is an autoimmune disorder following histopathologic review of the tissue involved under the microscope. In autoimmune disorders, the body’s natural defenses (antibodies and T-cells) fight its own tissue, mistaking it for foreign organisms for no apparent reason.
Some researchers believe that Rasmussen encephalitis may be triggered by an unidentified infection such as influenza, measles, or cytomegalovirus.
Rasmussen encephalitis mostly affects children ten years of age and younger. It is unusual to affect children under two years of age. Adolescents and young adults in much smaller proportions are also affected. There may be a history of some prior mild cold or flu prior to the onset of the seizures. The annual number of new-onset Rasmussen has been estimated as 2.4/10,000,000 persons less than or equal to 18 years of age.
Rasmussen encephalitis may be diagnosed clinically based upon a thorough clinical evaluation, a detailed patient history, and a complete neurological evaluation including advanced techniques such as electroencephalography (EEG), and magnetic resonance imaging (MRI).
During an EEG, the brain’s electrical impulses are recorded. Such studies may reveal brain wave patterns that are characteristic of certain types of epilepsy. During MRI, a magnetic field and radio waves are used to create cross-sectional detailed images of the brain. It is usual that the diagnosis is made after a minimum of two scans which will detail progressive shrinkage of the affected side of the brain.
Treatment of Rasmussen encephalitis is mostly symptomatic and supportive. Special services that may be beneficial to affected children include special social support, physical therapy, and other medical, social, and/or vocational services.
Various anti-seizure medications (anticonvulsants) may be prescribed to treat seizures. However, in most cases, anticonvulsants have proven ineffective. Medical treatments targeted at possible autoimmune disease may be tried, including steroids, immunoglobulin and tacrolimus. Immunological therapies (tacrolimus, intravenous immunoglobulins, potentially others as well) may slow down the neurological and structural deterioration but usually does not improve the epilepsy or progressive brain atrophy. Its precise role in management of Rasmussen encephalitis remains to be determined.
Surgery usually in the form of a cerebral hemispherectomy is the only way to cure the seizures and halt neurodevelopmental regression. However, there is the inevitable resultant functional deficits including hemiparesis (weakness of one side) and hemifield defect (impairment of vision to one side), and where the dominant side of the brain is affected, there may be an effect on language. The difficulty is often deciding on the necessary and best timing of surgery, dependent on the severity of epilepsy and degree of effect on learning and progression of the disease. The decision needs to be made jointly by the family and specialist center who deal with this condition regularly.
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Contacts for additional information about Rasmussen encephalitis:
Gary W. Mathern, MD
The Davies endowed Chair for Epilepsy Research at UCLA
Professor and Neurosurgical Director, Pediatric Epilepsy Surgery Program
Departments of Neurosurgery and Psychiatry & Biobehavioral Medicine
Mattel Children’s Hospital
David Geffen School of Medicine
University of California, Los Angeles
William Davis Gaillard, MD
Professor, Pediatrics and Neurology
George Washington University School of Medicine
Critical Care Neurology
Children’s National Medical Center
Associate Director, Center for Neuroscience Research
Children’s Research Institute
Prof. J. Helen Cross
The Prince of Wales’s Chair of Childhood Epilepsy UCL-Institute of Child Health, Great Ormond Street Hospital for Children & Young Epilepsy
Head of Neurosciences Unit
UCL-Institute of Child Health
4/5 Long Yard
London WC1N 3LU
Telephone number: 0207 599 4105
Fax Number: 0207 430 0032
Anne Brown, PA
The Neville Epilepsy Centre
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NINDS Rasmussen’s Encephalitis Information Page. National Institute of Neurological Disorders and Strokes. National Institutes of Health. https://www.ninds.nih.gov/disorders/all-disorders/rasmussens-encephalitis-information-page Last Updated3/27/19. Accessed Sept. 17, 2019.
Rasmussen’s Encephalitis. The Hemispherectomy Foundation. http://hemifoundation.intuitwebsites.com/rasmussen.html Accessed Sept. 17, 2019.
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