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This retrospective study completed at a tertiary care center aimed to assess the monothermal caloric test (MCT) as a screening test, using the bithermal caloric test (BCT) as a reference. Additionally, it attempts to measure the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of a fixed inter-auricular difference (IAD) value for both cold and warm stimuli using water irrigation. Medical records of 259 patients referred for vestibular symptoms who underwent BCT with water irrigation were reviewed. Patients with bilateral vestibular weakness and caloric tests using air irrigation were excluded. BCT showed 40.9% unilateral weakness. Two formulas were used to determine the monothermal caloric asymmetry (MCA-1 and MCA-2). The measurement of agreement Kappa between the two formulas in comparison with BCT revealed moderate agreement at 0.54 and 0.53 for hot and cold stimulation, respectively. The monothermal warm stimulating test (MWST) using MCA-2 showed better results, with a sensitivity of 80%, specificity of 91%, PPV of 83.1%, and NPV of 89.2%. Thirty-four patients had horizontal spontaneous nystagmus (HSN) with a mean velocity of 2.25°/s. These patients showed better sensitivity but lower specificity after adjustment of HSN using the MCA-2 formula at warm temperatures. Therefore, they should complete the caloric test with cold irrigation to perform the BCT. MCT is efficient as a screening test if the warm stimulus is used with the MCA-2 formula fixed at 25%. If present, HSNs should be adjusted. Negative IAD (normal) in the absence or presence of adjusted HSN or slow-phase eye velocity ≤ 6°/s at each right and left warm stimulation should be accomplished by the BCT. [ABSTRACT FROM AUTHOR]

Purpose: The first aim of this review is to summarize recent ocular motor signs in pre-encephalopathy patients with nutritional deficiency at risk of thiamine deficiency. Timely recognition of thiamine depletion in these patients, who may have a normal brain MRI, could lead to appropriate management and prevention of Wernicke's encephalopathy (WE) with full recovery. The second aim is to incorporate recent diagnostic testing on the revised WE diagnostic criteria and the identification of patients who may show slow, partial, or no response to treatment. Recent Findings: Selective vulnerability of periventricular gray neurons in thiamine deficiency is well known. Involvement of the vestibular and abducens nuclei may precede encephalopathy. Studies have shown mild ophthalmoparesis and bilateral symmetric vestibular loss in thiamine deficiency. Moreover, quantitative data has shown decreased horizontal vestibulo-ocular reflex (VOR) gain and nystagmus, with a favorable response to timely treatment. Summary: Ophthalmoparesis, horizontal nystagmus, and decreased gain of the horizontal VOR, sparing the vertical VOR, may be present in the early pre-encephalopathy stage of thiamine deficiency. Rapid response to a loading dose of parenteral thiamine might be seen in some cases and normalization, albeit slower in others. In contrast, analogous to the Korsakoff's syndrome, ocular motor and vestibular abnormalities may show only partial improvement. Future studies in larger populations at risk are needed to confirm the results of these preliminary observations. [ABSTRACT FROM AUTHOR]