Self-similar breakup of near-inviscid liquids.

The final stages of pinchoff and breakup of dripping droplets of near-inviscid Newtonian fluids are studied experimentally for pure water and ethanol. High-speed imaging and image analysis are used to determine the angle and the minimum neck size of the cone-shaped extrema of the ligaments attached to dripping droplets in the final microseconds before pinchoff. The angle is shown to steadily approach the value of 18.0 ± 0.4°, independently of the initial flow conditions or the type of breakup. The filament thins and necks following a τ(2/3) law in terms of the time remaining until pinchoff, regardless of the initial conditions. The observed behavior confirms theoretical predictions.

The natural history and growth rate of asymptomatic meningiomas: a review of 60 patients.

Little is known about the natural history and growth rate of asymptomatic meningiomas. To better delineate this problem, the authors reviewed the clinical records and imaging studies of the last 60 patients diagnosed with asymptomatic meningiomas at their institution. There were 45 women and 15 men, whose ages ranged from 38 to 84 years, with a mean age of 66 years. The most common tumor location was convexity (25 patients), but virtually all locations were represented. Three patients were lost to follow up. The average clinical follow-up review of the remaining 57 patients was 32 months (range 6 months to 15 years). None of the patients became symptomatic from an enlarging tumor during their follow-up period. Typically, once a meningioma was diagnosed, follow-up scans were obtained at 3 months, 9 months, and then yearly or every other year thereafter. Forty-five patients underwent follow-up scans, with comparison of tumor size to that found on the initial scan, over a period ranging from 3 months to 15 years. Thirty-five patients have shown no growth in their tumor size, with an average imaging follow up of 29 months (range 3-72 months). Ten patients have shown tumor growth calculated as an increase in the maximum diameter of the tumor. This growth ranged from 0.2 cm over 180 months to 1 cm over 12 months, with an average of 0.24 cm per year. Average imaging follow up for these patients was 47 months (range 6 months to 15 years). The authors conclude that patients with asymptomatic meningiomas need close clinical and radiological follow up to rule out other disease processes and to rule out rapidly enlarging tumors. Although the average follow-up time was short, the vast majority of these tumors appeared to show minimal or no growth over periods of time measured in years. With modern noninvasive imaging techniques, these tumors can be safely observed until they enlarge significantly or become symptomatic.

The use of PET in evaluating patients with primary brain tumours: is it useful?

During an 18 month period 39 patients were evaluated with [18F] fluorodeoxyglucose-PET (FDG-PET) for primary brain tumours. These included patients with suspected newly diagnosed tumours and patients with known tumours who were being evaluated for possible recurrence or increasing tumour grade. Scans were performed on a 951-31 Siemen's PET scanner with 4 mm resolution. Scanning time was about 20 minutes per patient. All patients had undergone recent cerebral MRI. These patients were divided into two groups. In the first group (30) MRI and PET concurred on the diagnosis. The second group (nine) comprised those where the interpretation of MRI and PET was different or there was a question of the diagnosis on MRI. This group comprised three patients in whom MRI suggested recurrent tumour and PET inaccurately suggested radiation necrosis; two patients with newly diagnosed enhancing lesions on MRI in whom PET was useful in distinguishing strokes from tumour; two patients with prior gliomas with new enhancing isolated lesions on MRI in whom PET scan accurately depicted radiation necrosis; and two patients with newly diagnosed enhancing lesions on MRI in whom PET scan was helpful in distinguishing multiple sclerosis from tumour in one but not in the other. Therefore, of the 39 patients, PET was helpful in five in distinguishing tumour from other disease processes; but, in so far as influencing treatment, it seemed helpful in only two. Thus PET seems to be of limited value as an aid to evaluating and treating patients with suspected or known primary brain tumours.

Surgical results in obese patients with sciatica.

A prospective study was done to determine the effect of obesity on the surgical results in patients with intractable sciatica. One hundred ten patients entered the study over an 8-month period. Five patients (1 obese) were excluded. Seventeen patients were included in the obese group. The two populations did not differ in age, sex, occupation, level of disc herniation, involvement of compensation, length of hospitalization, duration of disability, or incidence of surgical complications. At the 6-month follow-up assessment, 14 obese patients vs. 80 nonobese patients rated their surgical results good or excellent. Patients with postoperative weight loss were equally distributed between the groups. The data demonstrate that obesity should not be considered a prognostic factor when patients are eligible for surgical therapy.

Vertebral artery rupture associated with closed head injury. Report of two cases.

The authors report two patients with closed head injury who suffered laceration with rupture of the third portion of the vertebral artery. One patient died suddenly, with angiographic evidence of bilateral vertebral artery rupture. The mechanism of injury to the C1-2 segment of the vertebral artery relating to head and neck injury is discussed.

Microsurgical anatomy of the posterior inferior cerebellar artery.

Fifty cerebellar hemispheres from 25 adult cadavers were examined. The posterior inferior cerebellar artery (PICA), by definition, arose from the vertebral artery. The vertebral artery was present in 49 and the PICA was present in 42 of the 50 hemispheres. Forty-one of the 42 PICAs arose as a single trunk and 1 arose as a duplicate trunk. The PICA was divided into five segments: the anterior medullary segment lay on the front of the medulla; the lateral medullary segment coursed beside the medulla and extended to the origin of the glossopharyngeal, vagal, and accessory nerves; the tonsillomedullary segment coursed around the caudal half of the cerebellar tonsil; the telovelotonsillar segment coursed in the cleft between the tela choroidea and the inferior medullary velum rostrally and the superior pole of the cerebellar tonsil caudally; and the cortical segment was distributed to the cerebellar surface. Thirty-seven of the 42 PICAs bifurcated into a medial and a lateral trunk. The medial trunk supplied the vermis and the adjacent part of the hemisphere, and the lateral trunk supplied the cortical surface of the tonsil and the hemisphere. The PICA gave off perforating, choroidal, and cortical arteries. The cortical arteries were divided into vermian, tonsillar, and hemispheric groups. Sixteen of the 42 PICAs passed between the rootlets of the accessory nerve, 10 passed between the rootlets of the vagus nerve, 13 passed between the vagus and the accessory nerves, 2 coursed rostral to the glossopharyngeal nerve, and 1 passed between the glossopharyngeal and the vagus nerves.

Traumatic false aneurysm and carotid-cavernous fistula: a complication of sphenoidotomy.

Severe head injury with resultant basilar skull fracture is the most common etiology for traumatic false aneurysm of the cavernous carotid artery and for traumatic carotid-cavernous fistula. We present a case of false aneurysm and fistula that occurred as a complication of sphenoidotomy, fortunately a rare etiology of these two serious problems. Because of the current resurgence of trans-sphenoidal surgery, it is of utmost importance that all neurosurgeons possess an accurate and detailed knowledge of the anatomy of the carotid artery and its intracavernous route.