L Melzi

Evidence for retrochiasmatic tissue loss in Leber's hereditary optic neuropathy

Patients with Lebers hereditary optic neuropathy (LHON) have loss of central vision with severe damage of small‐caliber fibers of the papillomacular bundle and optic nerve atrophy. The aim of this study was to define the presence and topographical distribution of brain grey matter (GM) and white matter (WM) injury in LHON patients using voxel‐based morphometry (VBM). The correlation of such changes with neuro‐ophthalmologic findings and measurements of peripapillary retinal nerve fiber layer (RNFL) thickness by optical coherence tomography (OCT) was also assessed. Dual‐echo and fast‐field echo scans were acquired from 12 LHON patients and 12 matched controls. VBM analysis was performed using SPM5 and an ANCOVA model. A complete neuro‐ophthalmologic examination, including standardized automated Humphrey perimetry as well as average and temporal peripapillary RNFL thickness measurements were obtained in all the patients. Compared with controls, average peripapillary RNFL thickness was significantly decreased in LHON patients. LHON patients also had significant reduced GM volume in the bilateral primary visual cortex, and reduced WM volume in the optic chiasm, optic tract, and several areas located in the optic radiations (OR), bilaterally. Visual cortex and OR atrophy were significantly correlated with average and temporal peripapillary RNFL thickness (P < 0.001; r values ranging from 0.76 to 0.89). Brain damage in patients with LHON is not limited to the anterior visual pathways, but extends posteriorly to the OR and the primary visual cortex. Such a damage to the posterior parts of the visual pathways may be due either to trans‐synaptic degeneration secondary to neuroaxonal damage in the retina and optic nerve or to local mitochondrial dysfunction. Hum Brain Mapp, 2010.

A longitudinal conventional and magnetization transfer magnetic resonance imaging study of optic neuritis

Eleven consecutive patients with a first episode of acute optic neuritis were evaluated, using conventional and magnetization transfer (MT) magnetic resonance imaging (MRI), in order to assess the temporal evolution of optic nerve (ON) damage and to investigate the correlation of ON damage with visual outcome and electrophysiological parameters. Patients underwent neuro-ophthalmological, neurological, electrophysiological, and MRI assessments at baseline and after three and 12 months. ON volumes were measured on coronal T1–weighted images using a local thresholding segmentation technique. MT ratio (MTR) from the ON was derived from gradient echo images. No significant volume difference was detected between affected and healthy ON, both at baseline and follow-up. At baseline, mean MTR values were significantly higher in affected ON than in healthy ON (P = 0.001), whereas at months 3 and 12, the mean MTR values were significantly reduced in the affected ON (P = 0.02 and 0.003, respectively). Mean MTR of the affected ON, corrected for healthy ON values, progressively decreased over time (P = 0.04 at month 3 and P = 0.0012 at month 12). On the contrary, MTR values of healthy ON remained stable. No correlations were found between MTR measures and clinical or electrophysiological data. This study shows the presence of subtle pathological changes, possibly due to residual demyelination and subsequent additional demyelination and impaired remyelination, in the ON of patients with a first episode of optic neuritis. In the early phase of optic neuritis, MT MRI is more sensitive than atrophy measurements in detecting disease-related changes. Multiple Sclerosis 2007; 13: 265–268. http://msj.sagepub.com

Which Differences in Priming Effect Between Neglect and Hemianopia? A Case Description of a Bilateral Brain-Lesioned Patient

ABSTRACT It is widely known that visuospatial neglect and hemianopia maybe superimposed. We considered the differences in implicit information processing which is effective in patients with neglect but not with hemianopia. We then hypothesize that a prime-word in the neglected field should determine a semantic activation effect but not in a blind hemifield. Moreover eye movements could provide further details. In this work we considered a patient with a bilateral with the presence of either a left visual neglect and a right homonymous hemianopia. Our results supported implicit information processing in the space affected by neglect but not by hemianopia.