Errors in intraocular lens power calculation after photorefractive keratectomy.
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Aged↗
Biomedical subjects
K W Whittaker
Publications and source records attributed to K W Whittaker.
Compound anterior cranial base fractures: classification using computerized tomography scanning as a basis for selection of patients for dural repair.
OBJECT: A classification is proposed to organize anterior cranial base fractures systematically according to their location and size. The goal of this study was to determine whether these two variables, irrespective of cerebrospinal fluid (CSF) rhinorrhea, are related to the long-term risk of posttraumatic meningitis and, hence, to standardize decision making concerning surgical repair of associated CSF fistulas. METHODS: With the aid of high-resolution thin-section coronal computerized tomography (CT) scanning, anterior cranial base fractures were classified into the following four major types: I, cribriform; II, frontoethmoidal; III, lateral frontal; and IV, complex (any combination of the other three types). Fractures with a maximum bone displacement that extended farther than 1 cm in any plane were classified as "large" and those less than 1 cm as "small." The authors used this classification in a study of 48 patients who were treated by conservative (20 patients) or surgical (28 patients) means. The results showed a gradation of risk: the fracture most likely to develop infection was a large cribriform (Type I) and the least likely was a small lateral frontal (Type II). Statistical analysis showed that the trend for an increased infection rate was related to the cumulative effect of three variables in the following order: 1) prolonged duration of rhinorrhea (analysis of variance [ANOVA], p = 0.017); 2) large size of fracture displacement (ANOVA, p = 0.079); and 3) fracture's proximity to the midline (ANOVA, p = 0.015). CONCLUSIONS: In this series, microsurgical repair was accompanied by a minimum complication rate. Hence, the authors recommend that patients with fractures that combine the aforementioned variables should be considered to have a high long-term risk of infection and their injury should be surgically repaired as soon as the posttraumatic edema has subsided. This applies to the following fractures: large cribriform (Type I) with transient rhinorrhea lasting 5 to 8 days and large frontoethmoidal (Type II) with prolonged rhinorrhea lasting longer than 8 days. Furthermore, the authors conclude that this classification can improve the management of posttraumatic CSF fistulas of the anterior cranial base and may provide insights into the mechanisms underlying their spontaneous repair and susceptibility to meningitis.
Adolescent↗
Syndromes of posttraumatic neurological deterioration in children with no focal lesions revealed by cerebral imaging: evidence for a trigeminovascular pathophysiology.
PURPOSE: To explain the pathophysiology of the neurological deterioration that occurs after trivial head injuries in children and that is not caused by focal structural brain damage. Symptoms and/or signs include headache, confusion, drowsiness, vomiting, hemiparesis, cortical blindness, and seizures. CONCEPT: We propose that children who are susceptible to such neurological attacks have an unstable "trigeminovascular reflex," which is activated by craniofacial trauma. RATIONALE: After posttraumatic mechanical stimulation and activation of a defective or immature "excitable" trigeminovascular system, release of perivascular vasodilatory peptides causes cerebral hyperemia, which underlies the neurological deterioration. DISCUSSION: The original assumption that underlying cerebral edema was responsible for these phenomena has been proven incorrect by computed tomography. Subsequent proposed pathophysiological mechanisms include cortical spreading depression and trauma-triggered migraine. Recent research has implicated the trigeminovascular pathways in both these conditions and documented that head trauma can be associated with noncongestive cerebral hyperemia (i.e., not causing swelling). Thus, we propose that head trauma activates trigeminal nerve endings in face, scalp, dura, or cortex and, via a reflex, causes intracranial vasodilation and cerebral hyperemia. Drugs that block trigeminovascular activation might offer a benefit.
Blindness, Cortical↗
Logistics of performing an ophthalmic assessment in elderly inpatients.
To assess the feasibility of performing an ophthalmic assessment on elderly inpatients, we examined 48 patients over 75 years of age who were consecutively admitted to an acute elderly-care ward. Difficulties were encountered in 35 patients (73%). By employing simple methods to overcome these problems, useful information was obtained in all cases and the time taken to complete the examination ranged from six to 20 minutes (mean 7.5 minutes). Doctors looking after elderly patients should be encouraged to assess visual function and must not be deterred by anticipated logistical difficulties.
Aged↗
Perfluorocarbons: recent developments and implications for neurosurgery.
Over the last 30 years, perfluorocarbons (PFCs) have been extensively investigated as oxygen carriers. Early studies indicated that these compounds could be used as blood substitutes or protective agents against ischemia. Adverse characteristics such as instability, short intravascular half-life, and uncertainties concerning possible toxicity precluded wide clinical application. However, advances in PFC technology have led to the development of improved second-generation oxygen carriers that incorporate well-tolerated emulsifiers (egg-yolk phospholipids). The authors review recent developments in this field and consider the potential role of PFCs in future neurosurgical practice. Diagnostic applications could include their use to assess cerebral blood flow, local oxygen tension, and brain metabolism or to achieve enhanced imaging and precise staging of inflammatory, neoplastic, or vascular disease processes by means of computerized tomography, ultrasonography, and magnetic resonance studies. Therapeutic applications could include cerebral protection, an adjunctive role in radiotherapy of malignant brain tumors, protection against air embolism, the preservation of organs for transplantation, and ventilatory support in head-injured patients with compromised lung function. In addition, PFCs have been used successfully as a tool in ophthalmic microsurgery and potentially they could fulfill a similar role in microneurosurgery.
Emulsions↗