Acute hemorrhagic leukoencephalitis (AHLE) is a rare form of acute disseminated encephalomyelitis that is characterized by a brief yet intense inflammation in the brain and spinal cord. This attack critically damages the myelin, a protective covering of the nerve fibers.
There is poor prognosis for acute hemorrhagic leukoencephalitis because the onset of symptoms rapidly deteriorates the body, causing death in a span of a few days to one week. The mortality rate for this disease is approximately 70%.
Also known as Weston-Hurst syndrome, AHLE may be experienced both by children and adults. Since the development of the condition is abrupt, no prior determining symptoms can be observed. The onset of AHLE symptoms appear simultaneously as the disease progresses, making it an extremely difficult condition to treat. Nevertheless, many current researches and clinical experiments are dedicated to developing appropriate and long-term interventions for the disease.
Causes of AHLE
The exact cause of AHLE is unknown; however, researchers have found a link between the onset of symptoms and viral or bacterial inflammation. As such, it is hypothesized that AHLE develops as an autoimmune response to virus or bacteria.
In particular, when there is cross-reactivity between human myelin antigens and viral or bacterial antigens, demyelination occurs, making the protective unit of the nerve fibers collapse. This is an abnormal immune reaction since autoimmune processes usually target the central nervous system, but not the peripheral nervous system. In the case of AHLE, both areas of the nervous system are targeted.
In a recent study, researchers found support for this hypothesis when they injected a Theiler’s murine encephalomyelitis virus in mice. The experiment saw the activation of CD8+T cells in C57BL/6 mice, leading to the development of hemorrhagic demyelination within 24 hours. This experiment demonstrated the first murine model of AHLE.
Meanwhile, several studies have also found a weak link between the condition and vaccination for rabies or measles; however, this path is still in need of more confirmatory research.
Symptoms and Diagnosis of AHLE
Patients diagnosed with AHLE would usually present with fever, fatigue, headache, neck stiffness, nausea, seizures, vomiting, or coma. Brain hemorrhage, leading to damage of the white matter, is also observed. Along with these symptoms, other co-morbid medical conditions may be present in patients diagnosed with AHLE:
- Respiratory infection
- Focal neurologic signs
- Abdominal pain
- Gaze deviation
- Altered state of consciousness
- Sensory changes
- Motor weakness
- Aphasia in older patients
Case studies on AHLE found that patients diagnosed with multiple sclerosis (MS) and novel influenza AH1N1 are also prone to developing AHLE.
Diagnosis of AHLE is done using serial magnetic resonance imaging and brain biopsy. A positive diagnosis of the condition would show mass-like lesions, and edematous swelling that localizes in various brain areas. These two presentations may greatly affect white matter and the corpus callosum.
Immediate determination of the clinical presentation and the cerebrospinal profile are critical in quickly and appropriately diagnosing the condition. Researchers are trying to device methods wherein more common symptoms (such as headache, vomiting, or fever) could be excluded in the diagnostic process. This method would then focus on more characteristic features of AHLE for quicker diagnosis. A method called pathologic diagnosis is being culture-fitted to suit the needs for appropriate AHLE identification.
There are currently no direct interventions available for treating AHLE.
Case studies have found that administering high-dose corticosteroid therapy may potentially relieve patients from the progression of AHLE. While no prospective evaluation of such therapy was performed for AHLE patients, the intervention may be deemed therapeutic following the principle that corticosteroids decrease the autoreactive lymphocyte responses which initiate demyelination.
Reviewed by HH Patel, M.Pharm.