Biomedical subjects
Publications and source records attributed to M R Levine.
Five cases of ocular firearm injuries are presented. A physical analysis of the gunshot wound characteristics, with representative examples, is highlighted. The important early and late complications are completely discussed. Appropriate management sequence, including complete evaluation, diagnostic testing, and surgical intervention, is outlined and discussed.
We present our experience in using artificial skin (Omniderm) in the prevention of early healing of a raw lid margin. The material is inert and acts properly for this procedure.
A simple model of a feedback loop controlling ventilation is analysed. This model is intended to describe the response of the system, initially at equilibrium, to a sudden fall in CO2 concentration in the lung, brought about by a deep sigh. A previous paper described the model in detail and the general method of analysis. Here we continue the discussion of stability, first in terms of local stability after a small displacement from equilibrium and then by computer simulation to illustrate the behaviour after large displacements. The local analysis is used to select representative sets of system parameters to illustrate the different types of trajectory obtained by computer simulation. When the equilibrium point is stable the response to a disturbance is overdamped, underdamped or critically damped. When the equilibrium point is unstable the system responds by going into a limit cycle. The transition between these two cases proceeds via a Hopf Bifurcation. The limit cycle type of ventilatory pattern, i.e. a periodic, underdamped waxing and waning of ventilation is commonly seen in premature infants and in term infants between 1 and 6 months of age.
The semicircular flap of Tenzel has proved to be an excellent reconstructive procedure for central eyelid defects. Although originally described for defects measuring half of the eyelid, we have found that it may be used for defects greater than 60% in the lower eyelid, if the lower eyelid retractors and inferior orbital septum are identified and severed from their attachments. This is the key factor in the mobilization and advancement of this flap. It may, in many circumstances, obviate the need for a more complicated reconstructive procedure.
Trichoepithelioma histologically resembles basal cell epithelioma, but only rarely do the two lesions coexist. The case reported here documents a patient with hereditary trichoepithelioma who presented with a basal cell epithelioma of the medial canthus invading the lower eyelid. The clinical and histologic features of both entities will be discussed, as well as the possibility of malignant transformation of a trichoepithelioma to a basal cell epithelioma.
Prolapse of conjunctiva from the superior cul-de-sac, an infrequent complication of levator resection surgery, has been observed by us to have occurred following craniofacial reconstruction for craniostenosis. Three cases of conjunctival prolapse are presented: two that followed maximal external levator resections, and one that occurred after a supraorbital rim advancement and a subsequent cerebrospinal fluid leak. The causes of conjunctival prolapse and its appropriate treatment are reviewed.
Explore the source record for details and available documents.
A rare case of primary amyloidosis of the lacrimal gland and orbit is described with correlate CT-scan findings. Differentiation of this lesion from other lacrimal gland masses is discussed.
A method of repositioning extruding silicone tubes is described by reintubation with a second Crawford intubation set. The method and indications are described.
Explore the source record for details and available documents.
Five cases of orbital varices are presented, demonstrating a surgical approach with the use of vascular clips. Three of four cases were clipped at the apex of the orbit, with no recurrence. A fourth case was clipped two-thirds of the way back in the orbit, with no progression of the varix and significant improvement of the patient's symptoms. A fifth case failed because of extensive hemorrhaging. Follow-up ranged from 2 to 9 years.
Pseudotumor of the orbit is an uncommon entity in children. Three patients under 20 years of age with biopsy-proved orbital pseudotumor are presented. A three-month-old infant, to our knowledge the youngest patient reported with orbital pseudotumor, had a history similar to those of previously reported cases, whereas the two older patients differed from previously reported cases of childhood pseudotumor in that they lacked constitutional symptoms and orbital pain. Two of the patients were successfully treated with systemic steroids. In one patient, radiation therapy was required to reduce the mass.
Serial measurements of respiration in infants from birth to 7 months have revealed a changing pattern of response with age to spontaneous transient disturbances (e.g. deep sighs). These responses may be interpreted in terms of changing stability of the respiratory control system. The simplest possible model of respiratory control is analysed here. The control system is described by a feedback loop comprising a lung compartment, central and peripheral CO2 detectors and a circulatory delay. The differential equations representing this model are analysed in terms of the phase portrait. First we define the bounds of the solutions in the phase space and the equilibrium points. Next we discuss the local stability and damping of the system under small displacements from these equilibrium points. This local stability can be described in terms of the solution of a linear approximation about the equilibrium points. The trajectories of the solution vector under larger displacements from the equilibrium points are discussed in terms of Taylor expansions. It is shown by this analyses that this simple model can account qualitatively for the observed patterns of respiration following a deep sigh and the changes in that response from birth to 7 months.
Serial respiratory recordings using impedance pneumography and barometric plethysmography were made from shortly after birth to 7 months in fifteen normal full-term infants. Each recording was made with the infant asleep and sleep state was estimated from records of electroencephalogram and electro-oculogram made in parallel. The respiratory records obtained during non-rapid eye movement (r.e.m.) sleep were analysed with computer assistance and stretches of the record, approximately 1 min before and up to 2 min after a spontaneous sigh and ensuing apnoeic pause, were processed and presented as sequential values of the fractional deviation of VE, the breath by breath minute volume, from the mean. That part of the sequence which represented the respiratory response to the sigh was then fitted with second order equations representing the critically or underdamped response. The results were presented for each curve in terms of xi, the damping ratio and omega n, the frequency of the undamped respiratory oscillation. Three-quarters of the responses could be so fitted with an error of 20% or less. The residual responses were mainly from infants within a few days of birth. In the youngest infants (4 days or less), the respiratory response to a sigh was highly stable but sluggish: during the period 4-8 days to 3-4 months, the oscillatory period diminished from ca. 25-12 s and respiration was potentially unstable since a small reduction in the damping factor would cause prolonged oscillation while, from 3-4 months, the more mature type of response which was stable with a rapid recovery supervened. The possible mechanisms responsible for this trend are discussed in terms of the factors thought to determine respiratory stability in the adult together with the possible relevance of the results to the normal process of respiratory adaptation at birth and to the respiratory difficulties encountered by some infants in the new-born period and early infancy.
An osteoma is a slow growing, bony tumor which forms in the sinuses of the skull. Presenting complaints include headaches, cerebral symptoms, or visual disturbances, depending upon the location of the tumor. This paper describes an unusual case of ethmoid sinus osteoma, with epiphora as the primary symptom; it also caused the failure of a previous dacryocystorhinostomy. This case illustrates the need for thorough evaluation of epiphora, including sinus x-rays.
Jones' tubes were placed in 40 patients with canalicular obstruction and epiphora. Thirty of 35 patients (85.7%) followed up for two to 86 months had good results. There were five failures due to granulation tissue formation, diplopia, and patient dissatisfaction.
The Merkel cell is a distinctive nondendritic, nonkeratinocytic, epithelial clear cell believed to migrate from the neural crest to the epidermis and dermis, which is usually located in or near the basal layer of the epidermis and associated with nerve terminations. Merkel first described these cells in 1875 as "Tastzellen" occurring in the snout of a mole. They are believed to function as slowly adapting mechanoreceptors that mediate the sense of touch. Tumors arising from Merkel cells have been reported to occur on the head and neck area, the trunk, arms, and legs, and resemble a primary cutaneous lymphoma or cutaneous metastasis of a lymphoma or a carcinoma. Electron microscopy, to locate the characteristic membrane-bound, dense core neurosecretory granules, is needed for accurate diagnosis. These tumors must be treated aggressively to minimize the chance of local recurrence and nodal or visceral metastases. The authors present a case of Merkel cell tumor occurring on the eyelid. The clinical history, light and electron microscopic findings are shown.
Diagnosis to differentiate successfully an uncommon epidermoid carcinoma of the lacrimal sac from the commoner acute inflammation of the lacrimal sac requires a good history and thorough physical examination. If epidermoid carcinoma of the lacrimal sac is suspected, additional procedures including a dacryocystogram, orbital tomograms, plain films and CAT scans, and otolaryngologic consultation are necessary. Such a successful diagnosis of an epidermoid carcinoma of the lacrimal sac is reported here. An aggressive surgical approach is described and strongly recommended because review of the literature shows that the prognosis for these tumors is very grave.