Wernicke encephalopathy is a potentially life-threatening condition of abnormal carbohydrate metabolism occurring on the grounds of thiamine deficiency. Alcohol abuse, which impairs thiamine absorption, is often the underlying cause. Principal symptoms are ophthalmoplegia, ataxia and acute changes in consciousness. The diagnosis is often missed, which is why a thorough clinical and laboratory workup is necessary to recognize it early on.
Signs and symptoms of Wernicke encephalopathy (WE) stem from alterations of carbohydrate metabolism (inadequate absorption, accelerated metabolism or increased intake) together with the deficiency of thiamine (vitamin B1), as thiamine is a vital coenzyme of the Krebs cycle, the key step in metabolism of carbohydrates and energy production [1] [2] [3] [4]. Conditions that disrupt this process include hyperemesis (especially in pregnancy, known as hyperemesis gravidarum), acquired immunodeficiency syndrome (AIDS), administration of intravenous dextrose and other forms of parenteral nutrition, gastrointestinal tract (GI) surgery, but also malignancy and severe infections, all reducing the thiamine levels in the central nervous system (CNS) [1] [3] [5]. Chronic alcoholism, however, is by far the most widely recognized caused of WE, as a combination of poor diet, reduced storage of thiamine and long-term impairment of thiamine absorption from the GI tract [6]. Regardless of the cause, accumulation of toxic metabolites from impaired carbohydrate formation and degradation occurs, leading to a typical clinical presentation comprised of an altered mental state, ataxia, and ophthalmoplegia [4] [7]. Many reports have confirmed, however, that not all signs of WE may be present and that the diagnosis is often not recognized [1] [3] [4] [5] [7]. In fact, up to 68% of alcohol abusers and 94% of patients in whom alcoholism is not the cause of WE remain undiagnosed [1] [2]. WE can be life-threatening, as ischemia of the CNS can lead to irreversible neuronal damage or even death in the absence of an early diagnosis, which is why it is considered to be a medical emergency [1] [7].
The diagnosis of WE can be made only if clinical suspicion exists for this condition, which is based on findings obtained during history taking and a physical examination, the two most important parts of the workup. Information about preexisting conditions that could've caused WE may be provided either by the patient him/herself or from family members/friends if the patient presents with confusion and is unable to provide adequate answers, whereas the progression of symptoms is also of great importance. Moreover, gait disturbances, ophthalmoplegia or nystagmus, and an altered mental state are all confirmed during the physical examination, and the diagnosis should be suspected in all patients who present with two of the three mentioned symptoms accompanied by dietary insufficiency (known as the Caine criteria) [1] [2] [3] [4]. If clinical criteria are fulfilled, laboratory and imaging studies must be promptly employed to confirm WE. Although no specific markers in blood suggest WE, a thorough biochemical workup comprised of a complete blood count (CBC), liver and kidney function tests, serum electrolytes, arterial blood gas (ABG) analyses and evaluation of inflammatory parameters is vital. On the other hand, alterations in the T2 signal intensity in the mammillary bodies, periaqueductal areas, and the medial thalami are characteristic features of WE on magnetic resonance imaging (MRI), the recommended imaging study in this group of patients [1] [5] [7]. Signal intensities of the cerebellum, cerebral cortex, as well as cranial nerve, dentate, caudate and red nuclei are less common but reported signs of WE on MRI [5]. Thiamine levels are not routinely measured, as its exact concentration in the CNS cannot be determined based on serum values, indicating that the diagnosis rests on clinical and MRI findings.