Wernicke Encephalopathy

Introduction

Wernicke encephalopathy (WE) was first described in 1881 by Carl Wernicke as a “superior acute hemorrhagic polioencephalitis.” WE is now recognized as a complication of thiamine (vitamin B1) deficiency and results in the following clinical triad: mental confusion, gait ataxia, and ocular dysfunction. Diagnosing WE is straightforward when a known alcoholic demonstrates all of these symptoms. Unfortunately, this occurs in a minority of patients. One study investigating 245 patients over a 10-year period discovered that only 33% of patients demonstrated the complete triad. Consequently, WE is believed to be underdiagnosed.

The most common symptoms of WE are mental status abnormalities (82%), ocular dysfunction (29%), ataxia (23%), and polyneuropathy (11%). Mental status abnormalities include disorientation, indifference, and inattentiveness, with impaired learning and memory. Ocular abnormalities include nystagmus, bilateral cranial nerve VI palsies, and conjugate gaze palsies. Ataxia affects both stance and gait and is secondary to a combination of polyneuropathy, cerebellar involvement, and vestibular dysfunction. Korsakoff syndrome is a memory disturbance with amnesia and confabulation that may develop if the thiamine deficiency is left untreated.

WE can be identified at autopsy in 0.4% to 2.8% of the population. Aside from alcoholism, WE has been reported in a variety of conditions that disrupt thiamine absorption. Examples include following gastrointestinal surgery, prolonged vomiting, chemotherapy, systemic infections, noninfectious disease, and dietary imabalances.

Thiamine is needed for a variety of cellular processes including the maintenance of membrane osmotic gradients and glucose metabolism. With insufficient dietary intake, the human body’s stores become depleted in approximately 1 month. At histopathology, both vasogenic and cytotoxic edema can be identified, along with swelling of astrocytes and oligodendrocytes, proliferation of microglia, necrosis, demyelination, vascular proliferation, petechial hemorrhage, and disruption of the blood-brain barrier. The intravenous administration of thiamine is the treatment for WE. Importantly, glucose should never be administered without thiamine because doing so can precipitate or worsen WE.

Wernicke Encephalopathy Imaging Evolution: Overview

Optimal management of WE depends on a timely and accurate diagnosis. However, the diagnosis can be missed due to the disease’s occasionally subtle imaging findings, its temporal evolution, and the challenge of perceiving symmetric involvement of brain anatomy. Fortunately, characteristic imaging features within the appropriate clinical context can be used to confidently diagnose WE.

WE can be conceptually organized into early and late stages ( Fig. 5.1 ). Early WE begins with symmetric T2/FLAIR hyperintensity involving the thalami, mammillary bodies, hypothalamus, walls of the third ventricle, tectal plate, and periaqueductal gray matter. Contrast enhancement of the mammillary bodies can also be seen, is more common in alcoholic patients, and may be the only imaging finding. Contrast should therefore be administered when clinical suspicion is high ( Fig. 5.2 ). In late WE, mammillary body atrophy and enlargement of the third ventricle are seen ( Fig. 5.3 ). Cases demonstrating subtle T2/FLAIR hyperintensity isolated to the mammillary bodies and periaqueductal gray matter without involvement of the walls of the third ventricle or thalami, and without enhancement are less conclusive. Table 5.1 contrasts the differences in the imaging findings of early versus late WE.