Vascular accidents in preretinal arterial loops

Three cases with preretinal arterial loops complicated by obstructive accidents of various intensities are reported. The range of the complication varied from arterial spasm to transient retinal hemorrhages and arterial branch occlusion with permanent field defect, followed by extensive recurrent vitreous hemorrhages. These results lend further support to the assumption that the spiral arterial loops have an inherent tendency to twist and produce occlusive episodes.     

The fate of synaptic membranes of degenerating optic nerve terminals, and their role in the mechanism of trans-synaptic changes

Summary The fate of synaptic membranes of degenerating optic nerve terminals has been studied in the lateral geniculate nucleus of Rhesus monkey after eye enucleation. It was shown that pre-synaptic and post-synaptic membranes remain in close apposition to each other during all stages of degeneration and phagocytosis of affected terminals. As a result of this, fragments of presynaptic terminals were engulfed within glial processes, together with synaptic thickenings and parts of post-synaptic dendrites. On occasion small pieces of the degenerating terminals together with the synaptic membranes were engulfed by the post-synaptic dendrite. It is proposed that this pattern of removal of degenerating optic terminals results in injury to the post-synaptic cells, and triggers the transneuronal degeneration.     

A comparison of the mode of termination of the hippocampal and hypothalamic afferents to the septal nuclei as revealed by electron microscopy of degeneration

Summary Previous studies with the Nauta technique have established that fibres which originate in two important areas — the hippocampus and the hypothalamus — converge upon the cells of the septal nuclear complex. The purpose of this study was to investigate the anatomical basis of how the septal cells could differentiate between fibres from the two sources. Differences in the mode of termination of these two systems have been studied quantitatively at the electron microscope level by using the orthograde degeneration of terminals after lesions of the fimbria and the medial forebrain bundle. In the medial septal nucleus, the hippocampal fibres account for 35% of the terminals, and in the lateral septal nucleus, 43% of the terminals on the same side and a further 13% on the opposite side. These terminals are at least 98% axodendritic and 91% of them contain predominantly clear synaptic vesicles of 500 Å diameter. The hypothalamic fibres are the source of up to 19% of the axodendritic terminals in the medial septal nucleus, but considerably fewer in the lateral septal nucleus. In contrast to the hippocampal afferents, the hypothalamo-septal system has two characteristic features: firstly, the fibres give rise to up to 24% of the axosomatic terminals in the medial septal nucleus, and secondly, 63% of the terminals contain a population of vesicles with significantly higher proportions of dense centred vesicles of 800–1000 Å diameter.     

Retinal Detachments Following Intraocular Lens Implantation

Pseudophakic retinal detachments are more difficult to manage than the phakic variety, primarily because of increased difficulties in visualizing the peripheral retina. A review of the characteristics of 70 pseudophakic retinal detachments revealed that they were similar to those following routine cataract extraction, although we noted a mild tendency for periretinal membrane formation to be more commonly associated with the former group. Despite problems in viewing pseudophakic detachments, our data suggest that their repair rate closely approximates that for aphakic eyes, assuming allowances are made for the number of cases with significant peri retinal membranes that are accepted for surgery. Visual results following successful surgery may be somewhat lower than those in comparable aphakic eyes.     

Ophthalmological manifestations in VHL and NF 1: pathological and diagnostic implications

Von Hippel–Lindau disease (VHL) and neurofibromatosis type 1 (NF 1) are hereditary multitumor syndromes that show associated ocular manifestations. Capillary retinal angioma, a benign vascular tumor, is the classical ocular lesion in VHL. It often appears as the first manifestation of the disease and may thus lead to the diagnosis of VHL. Since small angiomas can be treated easily by laser photocoagulation, a regular ocular screening of VHL patients is recommended. Ocular manifestations of NF 1 are more diverse as compared to VHL. Lisch nodules of the iris are an important diagnostic criteria of NF 1 since they can be found in almost every affected patient. Optic glioma can occur both intraorbitally and intracranially. The intraorbital form causes progressive protrusion of the globe and eventually blindness. Extension of the tumor beyond the chiasm worsens the prognosis quoad vitam. The hallmark of NF 1, namely cutaneous neurofibroma can cause visual impairment when affecting the skin of the eyelids. The rare intraorbital pexiform neurofibroma is associated with abnormal development of the orbital bones and infantile glaucoma. It may result in orbital mass effects and therefore may need surgical excision.     

Toxicity and detoxification of lipid-derived aldehydes in cultured retinal pigmented epithelial cells

Age-related macular degeneration (ARMD) is the leading cause of blindness in the developed world and yet its pathogenesis remains poorly understood. Retina has high levels of polyunsaturated fatty acids (PUFAs) and functions under conditions of oxidative stress. To investigate whether peroxidative products of PUFAs induce apoptosis in retinal pigmented epithelial (RPE) cells and possibly contribute to ARMD, human retinal pigmented epithelial cells (ARPE-19) were exposed to micromolar concentrations of H2O2, 4-hydroxynonenal (HNE) and 4-hydroxyhexenal (HHE). A concentration- and time-dependent increase in H2O2-, HNE-, and HHE-induced apoptosis was observed when monitored by quantifying DNA fragmentation as determined by ELISA, flow cytometry, and Hoechst staining. The broad-spectrum inhibitor of apoptosis Z-VAD inhibited apoptosis. Treatment of RPE cells with a thionein peptide prior to exposure to H2O2 or HNE reduced the formation of protein-HNE adducts as well as alteration in mitochondrial membrane potential and apoptosis. Using 3H-HNE, various metabolic pathways to detoxify HNE by ARPE-19 cells were studied. The metabolites were separated by HPLC and characterized by ElectroSpray Ionization-Mass Spectrometry (ESI-MS) and gas chromatography-MS. Three main metabolic routes of HNE detoxification were detected: (1) conjugation with glutathione (GSH) to form GS-HNE, catalyzed by glutathione-S-transferase (GST), (2) reduction of GS-HNE catalyzed by aldose reductase, and (3) oxidation of HNE catalyzed by aldehyde dehydrogenase (ALDH). Preventing HNE formation by a combined strategy of antioxidants, scavenging HNE by thionein peptide, and inhibiting apoptosis by caspase inhibitors may offer a potential therapy to limit retinal degeneration in ARMD.     

Ipsilateral mamillary body atrophy after infarction of the posterior cerebral artery territory: MR imaging

We describe herein magnetic resonance (MR) features of ipsilateral mamillary body atrophy after infarction of the posterior cerebral artery (PCA) territory. During the period May 2000 through July 2004, 13 patients with infarction of the PCA territory underwent cranial MR imaging in the chronic stage. Two 1.5-T scanners were used to obtain axial T1- and T2-weighted images with conventional spin-echo and fast spin-echo pulse sequences, respectively. The slice thickness was 6 mm, with a 2-mm interslice gap. Five of the 13 patients with PCA territory infarction had ipsilateral mamillary body atrophy. However, this asymmetry of the mamillary bodies was unclear in two of the five patients because of the thickness of the axial image slices. All five patients had a temporo–parieto–occipital infarction. The remaining eight patients had a parieto–occipital or an occipital infarction. Unilateral transneuronal mamillary body degeneration after infarction of the ipsilateral PCA territory including the posteromedial temporal lobe can be detected on conventional thick axial MR images.     

Asymmetric atrophy of the supraspinatus muscle following tendon tear.

Muscle atrophy is a known consequence of muscle disuse, muscle denervation and tendon tear. Whereas after nerve injury muscle atrophies in the denervated area, the distribution of muscle atrophy following tear of its tendon is not known. Standardized MRI scans of 64 consecutive, painful shoulders were evaluated for supraspinatus tendon tearing, myotendinous retraction, supraspinatus muscle atrophy, fatty infiltration, ratio of the scapular (deep) and fascial (superficial) muscle area ("symmetry") and position of the central tendon within the supraspinatus fossa. There were thirteen shoulders with no and eleven shoulders with partial thickness supraspinatus tendon tears. In the forty cases with full thickness tendon tear, there was significant muscle atrophy and fatty infiltration. Atrophy of the fascial muscle portion was 43%, on the bony side it was 9% (p<0.005). The position of the central tendon within the supraspinatus fossa, was unaltered. Muscular changes following tendon tear occur highly asymmetrically: the muscle portion originating from the fascia primarily atrophies, the portion originating from the scapula primarily undergoes fatty infiltration. Muscular changes are not simply a consequence of muscle disuse, but dependent on architectural changes in the muscle.     

Thoracic herniation after lumbar spine fusion

We report on a 65-year-old male patient with rapid onset of incomplete paraparesis, based on a massive thoracic herniation following adjacent instability of the thoracolumbar spine after lumbar fusions with transpedicular instrumentation.     

The Acute Retinal Necrosis Syndrome: Part 2: Histopathology and Etiology

The acute retinal necrosis syndrome is manifested by diffuse uveitis, vitritis, retinal vasculitis, and acute necrotizing retinitis (see Part 1). We studied the histopathology and electron microscopic findings of an eye enucleated from a 67-year-old man with typical acute retinal necrosis. Histology showed profound acute necrosis of the retina, retinal arteritis, and eosinophilic intranuclear inclusions in retinal cells. Electron microscopy demonstrated a herpes group virus in all layers of affected retina. The implications of these findings for antiviral and other treatments are discussed.