Clinical Reasoning: A 17-Year-Old Girl With Progressive Cognitive Impairment

Abstract

A 17-year-old girl presented with a long history of cognitive impairment, personality and behavioral changes, dysarthria, and paroxysmal lower-extremity weakness. She was initially suspected of having mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes because of stroke-like symptoms, such as episodic lower-extremity weakness, as well as abnormal brain MRI findings of generalized cerebral atrophy, extensive high-intensity lesions in the cortex and subcortical white matter on fluid-attenuated inversion recovery images, decreased N-acetyl aspartate/creatine ratio, and a lactate peak in the focal area on spectrum images. However, there were no relatives with similar presentations in the family of the patient. The whole mitochondrial genome and whole-exome sequencing did not suggest pathogenic mutations, and no abnormalities were found in the blood or CSF lactate levels. In this case, we detail the clinical manifestations, diagnostic workup, and imaging findings. This case highlights the importance of assessing cognitive function and the relevant differential diagnoses in an adolescent with cognitive impairment.

Figure. Abnormalities of MRI of the Brain

T₁ MRI sequence revealed extensive cortical atrophy (A). Fluid-attenuated inversion recovery sequence showed multiple cortical and subcortical white matter hyperintense signal changes, mostly within the left frontoparietal and bilateral temporal lobes (B). MR spectroscopy demonstrated a decreased NAA/Cr ratio and lactate peak (arrow) in the focal area (C). Cr = creatine; NAA = N-acetyl aspartate.