The axonal damage marker tau protein in the cerebrospinal fluid is increased in patients with acute encephalopathy with biphasic seizures and late reduced diffusion.

Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) is a recently clinicoradiologically-established encephalopathy syndrome. In the present study, we examined the levels of cerebrospinal fluid (CSF) tau protein, a marker of axonal damage, in 11 patients with AESD. CSF tau levels were normal on day 1 and increased from day 3 of the disease between the initial and the secondary seizures. Magnetic resonance imaging (MRI) reveals reduced diffusion in the subcortical white matter during days 3-7. Two patients showed elevated tau protein prior to the diffusion abnormality of subcortical white matter on MRI. Levels of CSF neuron specific enolase (NSE), a neuronal marker, were elevated in only two out of seven patients with AESD, and CSF tau levels were also increased in these patients. Our results indicated that tau protein is a more sensitive marker than NSE and axonal damage causes the conspicuous MRI findings in AESD patients. A therapeutic strategy for axonal protection should be developed to prevent severe neurological impairment of AESD patients.