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Biomedical subjects

M A Spencer

Publications and source records attributed to M A Spencer.

4 recordsLinked to original sources
PubMed1995

Progressive hemifacial atrophy. A natural history study.

PURPOSE: To describe two very different natural history courses in 2 patients with hemifacial atrophy. Progressive hemifacial atrophy (Parry-Romberg syndrome, Romberg syndrome, PHA) is characterized by slowly progressive atrophy, frequently involving only one side of the face, primarily affecting the subcutaneous tissue and fat. The onset usually occurs during the first 2 decades of life. The cause and pathophysiology are unknown. Ophthalmic involvement is common, with progressive enophthalmos a frequent finding. Pupillary disturbances, heterochromia, uveitis, pigmentary disturbances of the ocular fundus, and restrictive strabismus have also been reported. Neurologic findings may be present, but the natural history and progression of ocular findings are often not described in the literature. METHODS: We studied the records and present findings of 2 patients with progressive hemifacial atrophy who were observed in our institution over a 10-year period. RESULTS: Both patients showed progression of ophthalmic findings, primarily on the affected side. One patient has had chronic uveitis with secondary cataract and glaucoma, in addition to retinal pigmentary changes. She also had a third-nerve paresis of the contralateral eye and mild seizure activity. The other patient had mild uveitis, some progression of unilateral retinal pigmentary changes, and a significant increase in hyperopia in the affected eye, in addition to hypotony at age 19 without a clear cause, but with secondary retinal and refractive changes. CONCLUSION: Ocular manifestations of progressive hemifacial atrophy are varied, but can progress from mild visual impairment to blindness.

Adult↗
PubMed1993

Biomechanical analysis of masticatory system configuration in Neandertals and Inuits.

Considerable debate has surrounded the adaptive significance of Neandertal craniofacial morphology. Numerous unique morphological features of this form have been interpreted as indicating an adaptation to intense anterior tooth use. Conversely, it has been argued that certain features related to muscle position imply a reduced mechanical advantage for producing bite forces on the incisors and canines. In this study, hypotheses about morphological specializations for anterior tooth use have been derived from a biomechanical model of Greaves (1978). These hypotheses were tested by performing separate pairwise comparisons of Neandertals and early Homo sapiens, and Inuits and Native Americans from Utah. Inuits are known to have produced repeated and high magnitude forces on their anterior dentition and therefore serve as a good model for a hominid adapted to intensive anterior tooth use. Biomechanically relevant dimensions of the masticatory system were measured using a computer-driven video analysis system and compared between the two taxa in each comparison. The results of this study reveal a number of similarities between the morphological specializations exhibited by Neandertals and Inuits that can be related to intensified anterior tooth use. The hypothesis that Neandertals were poorly designed for producing masticatory forces is rejected. Specializations that differ between the two groups are interpreted as being the result of differential functional demands placed on the postcanine dentition in Neandertals and Inuits. It is suggested that many of the unique morphological features of the Neandertal face are a response to intensified use of the anterior dentition and the need to retain a sufficiently large postcanine occlusal area necessary for a relatively high attrition diet.

Adaptation, Physiological↗