Subacute Sclerosing Panencephalitis (SSPE)

Symptoms typically occur years after infection, and, often, the first signs of SSPE are subtle—diminished performance in schoolwork, forgetfulness, temper tantrums, distractibility, and sleeplessness. However, hallucinations and myoclonic jerks may then occur, followed by generalized seizures. There is further intellectual decline and speech deterioration. Dystonic movements and transient opisthotonos occur.

Later, muscular rigidity, dysphagia, cortical blindness, and optic atrophy may occur. Focal chorioretinitis and other funduscopic abnormalities are common.

In the final phases, hypothalamic involvement may cause intermittent hyperthermia, diaphoresis, and pulse and blood pressure disturbances. Neurologic deterioration leading to coma and death can follow.

• Dyken's diagnostic criteria

• Serologic testing

• Electroencephalography (EEG)

• Neuroimaging

SSPE is suspected in young patients with dementia and neuromuscular irritability.

Formal diagnostic criteria (Dyken's criteria) exist for the diagnosis of SSPE. Two major criteria and one minor criterion are required for diagnosis (1, 2):

Major criteria:

• Anti-measles titres ≥ 1:4 in cerebrospinal fluid (CSF) or ≥ 1:256 in serum

• Typical (acute/rapidly, subacute, or chronic progressive disease, chronic relapsing-remitting disease) or atypical (seizures, presentation in infancy or adulthood, or prolonged early/subtle symptoms)

Minor criteria:

• Characteristic EEG findings

• Elevated CSF globulin levels

• Characteristic findings on brain biopsy

• Molecular genetic testing to detect mutated wild-type measles virus genome

EEG, CT or MRI, cerebrospinal fluid (CSF) examination, and measles serologic testing are performed. EEG shows periodic complexes with high-voltage diphasic waves occurring synchronously throughout the recording. CT or MRI may show cortical atrophy or white matter lesions. CSF examination usually reveals normal pressure, cell count, and total protein content; however, CSF globulin is almost always elevated, constituting up to 20 to 60% of CSF protein. Serum and CSF contain elevated levels of measles virus antibodies. Anti-measles IgG appears to increase as the disease progresses.

Subacute Sclerosing Panencephalitis (MRI Scans)

Image

This image shows MRI scans of the brain at the patient's time of presentation in the neurology clinic (panels 1 and 2) and 3 months later (panels 3 and 4).

Panels 1 and 3 are T1-weighted images, and 2 and 4 are T2-weighted images. The initial MRI scan (1 and 2) reveals a focal abnormality in the subcortical white matter of the left frontal lobe, consisting of a hypointense signal on the T1-weighted image (arrow in 1) and a hyperintense signal on the T2-weighted image (arrow in 2).

In the 3-month follow-up scan, the focal abnormality in the left frontal lobe is less obvious than previously (arrow in 4), but advanced and diffuse cortical atrophy is present, signified by the ventriculomegaly and markedly enlarged sulci (arrowheads in 3).

SCIENCE SOURCE / SCIENCE PHOTO LIBRARY

If test results are inconclusive, brain biopsy may be needed.

Molecular genetics may detect the causative mutated wild-type measles viral RNA genome.

The differential diagnosis includes a wide variety of viral and autoimmune encephalitides as well as neurodegenerative, metabolic, and neoplastic diseases.

• Supportive care

Antiseizure medications and other supportive measures are the only accepted treatments.

Antiviral and immunomodulatory medications, including isoprinosine, interferon alfa, IV immune globulin, ribavirin, and lamivudine, are used, but they have generally not proved helpful beyond modest or transient effects and are often not available in low-resource settings (1, 2).

The disease is almost invariably fatal, with a mortality rate of up to 95% within 1 to 3 years (often pneumonia is the terminal event), although some patients have a more protracted course (1, 2).