JOURNAL OF THE LOUISIANA STATE MEDICAL SOCIETY
the most common cause of ODS. 3,4 Furthermore, metabolic derangements of the liver may increase susceptibility to ODS. Recent publications describe predisposing conditions such as Wilson’s disease, 10 alpha-1-antitrypsin deficiency, and non- alcoholic steatohepatitis. 11 The manifestations of ODS indeed seem to be influenced by a multifactorial process, including a patient’s nutritional status, acute vs. chronic nature, and predisposing illnesses or conditions that may affect the involved metabolic pathways. Newer studies are underway to further delineate the exact mechanism and causes, including an increased interest in the role of inflammation. 12
of asymptomatic ODS to avoid attributing symptoms secondary to alternate neurological disorders, like stroke or neuropathy, to incidental pontine or extrapontine lesions. 16
CLINICAL PRESENTATION
A
B
Commonly ODS presents as a rapid deterioration several days following the restoration of normonatremia in a profoundly hyponatremic patient, usually a chronic alcoholic or one who has been chronically malnourished. Patients with various comorbidities, such as diabetes, renal disease, status post liver transplant, or post-surgical states, are also candidates for developing ODS upon fluid/electrolyte correction. 2 Patients with CPM develop symptoms of pseudobulbar paralysis, including dysphagia and dysarthria, acute para- or quadriparesis, and in rare cases, the progression to a locked-in state. 2 This state results from lesions in the pons involving the corticobulbar fibers, as well as the corticospinal tracts. Extrapontine myelinolysis has been shown to clinically manifest with a spectrum of extrapyramidal symptoms and movement disorders. Symmetric lesions similar to those identified in CPM have been found in the basal ganglia, cerebellum, lateral geniculate bodies, as well as in the external, extreme, and internal capsules. 13 Clinical findings corresponding to these extrapontine lesions could include mutism, parkinsonism, dystonia, and catatonia. 2 In a case report by Aaron de Souza, a 60-year-oldmale presented with hyponatremia and hypokalemia after 36 hours of emesis. His normonatremic state was restored at the recommended rate of sodium correction. Over the following three days, the patient developed an acute symmetric akinetic-rigid syndrome. 14 In this particular case of ODS, the patient’s symptoms were reflecting EPM, although on magnetic resonance imaging (MRI), typical lesions of CPMwere noted in the pons in addition to the bilateral lesions in the putamen and caudate. This example of diffuse ODS highlights the varied spectrumof clinical presentations that may not always correlate with the lesions identified on brain MRI. In recent publications, a number of cases of asymptomatic ODS have been reported that reflect an increased sensitivity of MRI in lesion detection, allowing for the incidental recognition of the disease without significant clinical manifestations yet developed. 15 Clinically, it is important to recognize the possibility
C
D
Figure 1. 51-year-old man with chronic alcoholism, malnutrition, hepatic and renal insufficiency, who presented with ataxia, spasticity, and diplopia, as well as memory and cognitive impairment. (A) Initial axial CT, non-enhancing, revealing no apparent abnormalities. Immediate follow-up MR (B) Axial T2 (C) Axial Diffusion weighted image (D) Coronal T2 revealing localized hyperintense signal within the pons.
IMAGE FINDINGS
In current practice, MRI is the definitive imagingmodality used in diagnosing ODS. CPM presents as a trident shaped lesion in the central pons with sparing of the more peripheral corticospinal tracts and ventrolateral tegmentum. The extrapontine lesions of ODS present symmetrically at various sites, including the basal ganglia, white matter, and cerebellum. 14 Classically the lesions of ODS are hypointense on T1-weighted, hyperintense on T2- weighted, hyperintense on Fluid-attenuated inversion recovery (FLAIR), and diffusion weighted imaging (DWI) sequences 17 (Figures 1 and 2). Less commonly, the lesion can demonstrates hyperintense signal on T1-weighted sequence, indicating coagulative necrosis. The lesions are non-enhancing on contrast enhanced MRI. 2 It has been shown that the extent of imaging findings depends on the time course of ODS, as development of MRI changes could be delayed in relation to the onset of clinical symptoms.
90 J La State Med Soc VOL 169 JULY/AUGUST 2017
Made with FlippingBook Digital Publishing Software