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Mitochondriopathies are a heterogeneous group of diseases with variable phenotypic presentation, which can range from subclinical to lethal forms. They are related either to DNA mutations or nuclear-encoded mitochondrial genes that affect the integrity and function of these organelles, compromising adenosine triphosphate (ATP) synthesis. Magnetic resonance (MR) is the most important imaging technique to detect structural and metabolic brain abnormalities in mitochondriopathies, although in some cases these studies may present normal results, or the identified brain abnormalities may be nonspecific. Magnetic resonance spectroscopy (MRS) enables the detection of high cerebral lactate levels, even when the brain has normal appearance by conventional MR scans. MRS is a useful tool for the diagnosis of mitochondriopathies, but must be correlated with clinical, neurophysiological, biochemical, histological, and molecular data to corroborate the diagnosis. Our aim is to clarify the most relevant issues related to the use of MRS in order to optimize its technical parameters, improving its use in the diagnosis of mitochondriopathies, which is often a challenge.

The "ears of the lynx" sign was previously reported as a neuroimaging finding observed in patients with autosomal recessive hereditary spastic paraplegia in association with a thin corpus callosum (ARHSP-TCC). We report a patient with a chronic form of Marchiafava-Bignami disease (MBD) that presented with this imaging feature. Diffusion tensor imaging (DTI) and fiber-tracking data support that this finding is a consequence of the structural derangement, which enlarges a preexisting border zone of the bundles of fibers from the corpus callosum (CC) genu to the forceps minor and anterior corona radiata. Therefore, we assume that despite their pathological differences, damage to the anterior portion of the CC is responsible for the imaging similarities between MBD and ARHSP-TCC.

Summary objective Hyperprolactinaemia is caused by high levels of monomeric, dimeric or macro forms of prolactin in circulation, the monomeric form being predominant in patients with prolactinomas. Macroprolactinaemia, however, is common and is associated with asymptomatic cases. In this study, we reviewed our records regarding clinical and imaging investigations in patients who were found to have hyperprolactinaemia predominantly due to the presence of macroprolactin and compared them with the findings observed in patients whose prolactin molecular size consisted predominantly of the monomeric form. patients and methods We conducted a retrospective study of 113 consecutive patients (nine men and 104 women, aged 19–67 years, median age 39 years) with hyperprolactinaemia who were screened for the presence of macroprolactin by polyethylene glycol precipitation and/or chromatography and submitted to pituitary magnetic resonance imaging (MRI) and/or computerized tomography (CT). results Fifty-two of 113 patients (46%) had hyperprolactinaemia due to macroprolactin, whereas the remaining 61 patients (54%) had their hyperprolactinaemia confirmed by the predominance of the monomeric form. Both groups shared similar mean prolactin levels (79·9 ± 63·6 µg/l, median of 62·0 µg/l, and 97·9 ± 155·4 µg/l, median of 61·0 µg/l, respectively). Of the patients with macroprolactinaemia, 46% had no symptoms of hyperprolactinaemia, whereas only 10% of the patients who screened negative for macroprolactin were asymptomatic. There was an association between macroprolactinaemia and negative pituitary imaging findings: normal pituitary images were found in 78·9% of patients who had macroprolactinaemia and in 25% of patients with monomeric hyperprolactinaemia. In addition, none of the patients with macroprolactinoma (seven cases) had macroprolactinaemia. conclusions The presence of macroprolactinaemia does not exclude the possibility of a pituitary adenoma and consequently may not prevent pituitary imaging studies. However, our data demonstrate that all asymptomatic patients who screened positive for macroprolactin had normal pituitary imaging studies. Patient samples showing hyperprolactinaemia should be first tested for macroprolactin, before the patient is submitted to imaging studies. We suggest that imaging studies should be ordered in patients with macroprolactinaemia when indicated by clinically relevant features. As a result, unnecessary anxiety and costly medical procedures may be prevented.