In general, patients are classified as having BBE rather than MFS if there is evidence of central involvement in the form of decreased consciousness or long tract signs, such as clonus, spasticity and hyper-reflexia. Odaka et al3 undertook a study to clarify the neurological features of 62 cases of BBE. Other common neurological features included facial weakness, bulbar palsy and nystagmus. There have also been case reports of patients with BBE presenting with hypersomnolence and decorticate posture, indicating CNS involvement.
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Miller Fisher described cases of ophthalmoplegia and ataxia in a edition of New England Journal of Medicine. But in contradistinction to BBE, these patients had no change in sensorium and almost universally these patients were areflexic.
The majority of patients achieved spontaneous recovery without the need for treatment despite the alarming initial presentation of BBE. The discovery that a large number of affected patients tested positive for the Anti-Gq1b antibody led to a greater understanding of BBE.
In this article we review some of the key features of BBE including pathophysiology, epidemiology, presentation and investigations, differential diagnosis, and management and treatment.
Pathophysiology BBE can occur without any preceding symptoms, but the majority of cases see a preceding infectious illness. In a review of cases of Anti-Gq1b Syndrome, antecedent illness was seen in 94 percent of patients, with upper respiratory tract infection being most common. Common seropositivity between these two conditions highlights their pathophysiological and clinical similarities. Anti-Gq1b antibody is one that interacts with the peripheral nerve ganglioside, Gq1b.
The precise incidence and prevalence of BBE in the United States and other Western nations is currently unknown, which can be attributed to the rarity of the disease and confusion and overlap with other Anti-Gq1b antibody syndromes. There is a lack of similar large-scale BBE epidemiological studies in Japan and in the rest of the world. An increased incidence in Japan and other Asian countries is observed in the summer months. Presentation and Clinical Investigation Our present day resources bear no clinical guidelines that describe specific diagnostic criteria for BBE.
However, most experts agree that the presence of signs and symptoms including acute bilateral ophthalmoplegia, ataxia, and altered sensorium are highly suggestive of the diagnosis.
It should be noted not all cases present classically with this triad of features, and absence of one does not rule out the diagnosis. Altered sensorium is variable where patients can present with drowsiness, stupor, or in the most severe cases, coma, which can be seen in up to 20 percent of cases. Ataxia most commonly presents with truncal and limb involvement, however solitary involvement can be seen as well. BBE can also present with dysarthria and either hyperreflexia or hyporeflexia on examination.
The diagnosis of BBE is largely based on clinical features, though additional studies may aid in making an accurate diagnosis. The most supportive laboratory investigation is positive Anti-Gq1b antibodies, especially in the setting of the appropriate clinical context. Yet it should be noted that negative antibody testing does not preclude the diagnosis: an analysis of 62 cases of BBE with a strict diagnostic criteria of acute symmetrical ophthalmoplegia, altered sensorium, and ataxia, anti-Gq1b antibodies were positive in 66 percent of patients.
EEG findings that can be seen include slow-wave activity in the to range, consistent with central nervous system involvement. In BBE MRI brain findings are variable, where imaging can be unremarkable or hypointense foci on Tweighted images and hyperintense foci on T2-weighted images can be seen.
Foci can be seen in the brainstem, which is expected, however thalamic and basal ganglia lesions have been documented as well. The association of BBE with Anti-Gq1b antibody syndrome is supported by infection being the mutual precipitant for a subsequent immune-mediated reaction. MFS usually presents with areflexia, consistent with a peripheral pathology.
Anti-Gq1b seropositivity has been witnessed in up to 83 percent of MFS cases9 whereas only about 66 percent of patients with BBE have demonstrated anti-Gq1b seropositivity.
Acute axonal neuropathy is characterized by an acute onset of symmetrical motor weakness, areflexia, and facial and oropharyngeal weakness. Acute axonal neuropathy is also commonly preceded by infection. Management and Treatment Effective management and treatment of BBE and other variants of Anti-Gq1b syndrome requires prompt recognition and diagnosis.
While the majority of patients with BBE and MFS achieve nearly complete recovery, a number of reported cases of recurrence exist. The majority of documented cases of BBE have shown patients to regain baseline functional status within 6 months of diagnosis. These patients have been shown to have a delayed onset of recovery for poorly understood reasons. A recent Cochrane review was not able to give any specific recommendations for the treatment of both BBE and MFS because of an apparent lack of randomized trials evaluating treatment in such clinical settings.
This interesting condition has characteristic signs and symptoms including altered sensorium that should be kept in mind in the setting of new onset ataxia. Our understanding of BBE has greatly evolved with the recognition of the role of Anti-Gq1b antibodies in its pathogenesis.
Anti- Gq1b antibody seropositivity has also suggested that BBE is most likely part of a spectrum of diseases under the umbrella known as Anti-Gq1b antibody syndrome. Despite improvements in the understanding of BBE, much more work remains to be done. More epidemiological studies of the incidence and prevalence of BBE should be performed in Western nations. There is also a need for randomized controlled trials to evaluate if certain therapeutic agents or procedures may hasten recovery for patients with BBE.
Odaka M. Brain Bickerstaff ER. Brainstem Encephalitis: further observation on a grave syndrome with benign prognosis. British Medical Journal Anti-Gq1b IgG antibody syndrome: clinical and immunological range. J Neurology, Neurosurgery, and Psychiatry Shahrizailla N. Bickerstaff brainstem encephalitis and Fisher Syndrome: anti-Gq1b antibody syndrome. Journal of Neurology, Neurosurgery, and Psychiatry. Winer JB. Journal of Neurology, Neurosurgery, and Psychiatry Aranyi Z. Miller Fisher syndrome: brief overview and update with a focus on electrophysiological findings.
European Journal of Neurology Koga M. Nationwide survey of patients in Japan with Bickerstaff brainstem encephalitis: epidemiological and clinical characteristics. J Neurology Neurosurgery Psychiatry Yuki N. Fisher syndrome and Bickerstaff brainstem encephalitis Fisher-Bickerstaff syndrome. J Neuroimmunology Ito M. Journal of Neurology Mondejar R R. MRI findings in a remitting-relapsing case of Bickerstaff encephalitis. Neuroradiology Nagashima T. JAMA Sharma V. Journal of Clinical Neuroscience Cochrane Database Syst Rev Journal of Neurological Science Shimokawa M.
Ther Apher TA Hardy. Journal of Neuroimmunology. Evans, MD and Christina L.
Bickerstaff brainstem encephalitis
Bickerstaff's Brainstem Encephalitis