Rabbit study of an in situ forming hydrogel vitreous substitute.

PURPOSE: An in situ forming hydrogel was evaluated as a potential vitreous substitute in rabbits. METHODS: The hydrogel used a disulfide cross-linker that was then reduced to produce an injectable thiol-containing polymer solution. The disulfide cross-links reformed by air oxidation of the thiols and produced a stable hydrogel once inside the eye. The polymer was clear, autoclavable, and could be stored easily in the presence of nitrogen gas. Capillary rheometry was used to measure the viscoelastic properties of the hydrogels and the porcine vitreous. Fourteen black rabbits underwent a pars plana, 25-gauge, three-port vitrectomy by a single surgeon with injection of a vitreous substitute. RESULTS: The refractive indices of the hydrogels were measured by refractometry and were shown to be close to 1.33, and the 2% hydrogel matched the mechanical properties of the natural vitreous humor. The reduced polymeric hydrogel was easily injectable through a small-gauge needle into the vitreous cavity and did not show any fragmentation. The material underwent gelation within the eye, remained optically clear, and appeared well tolerated clinically. Slit lamp examination, dilated fundus examination, and electroretinograms showed no evidence of vitritis, uveitis, or endophthalmitis after 1 week. Histopathologic evaluation did not reveal any overt toxicity or gross morphologic changes in the retina. CONCLUSIONS: The fact that this process of in situ gelation gives rise to hydrogels that are biocompatible and physically and optically similar to the natural vitreous suggests its suitability as a permanent vitreous substitute. Hydrogel candidates will be further studied to evaluate long-term biocompatibility and degradation in vivo.

Fatality in a case of envenomation by Crotalus adamanteus initially successfully treated with polyvalent ovine antivenom followed by recurrence of defibrinogenation syndrome.

INTRODUCTION: Recurrences of clinical or laboratory manifestations of North American pit viper envenomation may happen despite control of the envenomation syndrome by prompt and adequate antivenom therapy. Recurrences of coagulopathy in victims of Eastern diamondback rattlesnake envenomation are generally regarded as benign. The vast majority suffer no actual bleeding despite florid coagulation laboratory abnormalities due to selective defibrinogenation. CASE REPORT: We report what we believe to be the first fatality following successful control of the envenomation syndrome following ovine antivenom treatment resulting from envenomation by a bite from the Eastern diamondback rattlesnake. This case raises the question of whether such recurrences are in fact benign, causal, or coincidental. This patient sustained significant brain hemorrhage and death ensued due to generalized cerebral edema. Defibrinogenation occurred 4 days after treatment with ovine antivenom. DISCUSSION: Coagulation abnormalities following Eastern diamondback rattlesnake envenomation are due to selective defibrinogenation. This is separate from disseminated intravascular coagulation (DIC). Thrombin generation, thus hemostasis, are generally considered normal. This case may cause reexamination of this belief.

Tardive parkinsonism in a bipolar patient: post-mortem examination supports a physiological rather than pathological dysfunction.

We describe a case of tardive parkinsonism in the setting of bipolar syndrome, and we offer pathological confirmation that idiopathic Parkinson disease was not the underlying etiology. A 74-year-old Hispanic woman with a history of bipolar disease was noted to have oro-buccal-lingual chorea and parkinsonian symptoms such as resting tremor, rigidity, bradykinesia, and gait disorder persisting several months after neuroleptic discontinuation. She had minor improvement in ambulation with levodopa treatment, and she significantly improved in ambulation only during her manic states. Examination of the subject's post-mortem brain revealed no explicit evidence of degeneration in substantia nigra or other brainstem centers, and no nigral or cortical Lewy bodies were present. Glial cytoplasmic inclusions (characteristic of multiple systems atrophy) and globose neurofibrillary tangles (seen in progressive supranuclear palsy) were not seen either. This patient's presentation was most consistent with neuroleptic-induced parkinsonism and tardive dyskinesia; the etiology was likely related to previous neuroleptic exposure.

Progressive oculo-orofacial-speech apraxia (POOSA).

A loss of speech can be related to disorders of the motor units (paresis), language deficits (aphasia), or speech programming deficits (apraxia of speech). Although apraxia of speech has been reported to be associated with degenerative diseases, we observed a patient with a unique constellation of signs that included apraxia of speech, oculo-orofacial apraxia and a supranuclear ophthalmoplegia in the absence of extrapyramidal (Parkinsonian) signs. Post-mortem examination revealed a loss of neurons in the frontal and temporal regions, but there was also a marked loss of neurons and astrogliosis in the caudate, claustrum, globus pallidus, substantia nigra, and loss of axons in the anterior cerebral peduncles. This patient's clinical presentation and the pathological correlates suggest that he might have suffered with a distinct disorder we call progressive oculo-orofacial-speech apraxia or POOSA.

Isolated cranial nerve III palsy as the presenting manifestation of HIV-related large B-cell lymphoma: clinical, radiological and postmortem observations: report of a case and review of the literature.

Rarely can a neurologically isolated cranial nerve III palsy be the presenting manifestation of central nervous system lymphoma. We detail the clinical, radiological, and pathological features of a previously healthy 45-year-old man presenting with an isolated, pupil-involving, right cranial nerve III palsy due to human immunodefiency virus (HIV) related non-Hodgkin lymphoma. Magnetic resonance imaging demonstrated bilateral peripheral cranial nerve III enhancement with no brain parenchymal or leptomeningeal abnormalities. Cerebrospinal fluid analysis revealed a monocytic pleocytosis with an elevated protein concentration and depressed glucose level. Morphologic and flow cytometric analysis of the cerebrospinal fluid was compatible with a large B-cell lymphoma. Serologic tests for HIV were positive. Postmortem examination of the brain revealed malignant lymphomatous cell infiltration of both cranial nerve III, diffuse leptomeningeal disease and focal superficial subependymal and subpial invasion. Based on our review of the literature, we were able to find only 10 detailed cases of cranial nerve III palsy as the presenting manifestation of central nervous system lymphoma. Furthermore, none of the previously reported cases correlated the magnetic resonance imaging findings with the gross and histopathologic observations.

Isolated anisocoria from an endodermal cyst of the third cranial nerve mimicking an Adie's tonic pupil.

We present only the second reported case in the literature of a neuroenteric cyst involving the third cranial nerve. Our case is highlighted by the initial presentation of an isolated anisocoria, initially believed to represent an Adie's tonic pupil as interpreted by pharmacologic testing. False-positive results may occur with the dilute pilocarpine test.

beta-Catenin is expressed aberrantly in tumors expressing shadow cells. Pilomatricoma, craniopharyngioma, and calcifying odontogenic cyst.

We studied the beta-catenin immunohistochemical profile in tumors expressing shadow cells: pilomatricoma, 10 cases; calcifying odontogenic cyst, 6 cases; and craniopharyngioma, 9 cases. There was strong membranous, cytoplasmic, and nuclear staining of the immature basaloid cells in all of these tumors. Shadow cells were negative in all tumors. It has been documented that rising levels of free beta-catenin drive the formation of complexes with T-cell factor/lymphoid enhancer factor (TCF-Lef) and up-regulate the wingless-Wnt cell-cell signals. The end result is an abnormality of beta-catenin degradation and, thus, a buildup of free beta-catenin in the cytoplasm and/or nucleus, resulting in the stimulation of cellular proliferation and/or inhibition of cell death. beta-Catenin seems to have an important role in the oncogenesis of these tumors. The similar pattern of keratinization in these tumors and the similar pattern of beta-catenin immunoreactivity in the cytoplasm and the nucleus are important findings. It seems that the activation of a common cellular pathway, namely Wnt-beta-catenin-TCF-Lef, has a role in the pathogenesis of these tumors. The latter could be related to their shared method of keratinization or shared dysfunction of the cellular adhesion complex leading to tumorigenesis.

Progressive dementia and hypersomnolence with dream-enacting behavior: oneiric dementia.

BACKGROUND: Sleep disorders are associated with several types of degenerative dementias, including Alzheimer and prion diseases. Animal models have demonstrated abolition of rapid eye movement atonia, resulting in dream-enacting complex movements termed oneiric behavior, and patients with fatal familial insomnia may have vivid dreams that intrude on wakefulness. OBJECTIVE: To describe a new form of progressive dementia with hypersomnia and oneiric behavior. METHODS: Neuropsychological and polysomnographic studies of a middle-aged woman with a progressive dementia, excessive daytime sleepiness, and a vertical gaze palsy. RESULTS: Neuropsychological testing revealed decreased verbal fluency, impaired attention and working memory, amnesia, poor recall, and bradyphrenia with hypersomnia. Polysomnography revealed a rapid eye movement behavioral disorder with complete absence of slow wave sleep. Prion protein analysis did not reveal the mutation associated with fatal familial insomnia, and other diagnostic test findings were unrevealing. CONCLUSION: Our patient had a previously unreported syndrome of progressive dementia associated with rapid eye movement behavioral disorder and the absence of slow wave sleep.