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Biomedical subjects

A Yokoh

Publications and source records attributed to A Yokoh.

10 recordsLinked to original sources
PubMed1997

Rapidly-growing ectopic pituitary adenoma within the sphenoid sinus--case report.

A 75-year-old male with left abducens nerve paresis presented with an ectopic pituitary adenoma invading the posterior wall of the sphenoid sinus. The sphenoidal mass grew rapidly for 6 months with left ophthalmoplegia and was partially removed via the transsphenoidal approach. The histological examination showed a benign pituitary adenoma, but the MIB-1 proliferating cell index was 6.8%, reflecting the clinically malignant behavior. The symptom gradually improved without tumor regrowth over 1.5 years after conventional irradiation.

Adenoma↗
PubMed1996

Total capsular calcification in a prolactinoma--case report.

A 42-year-old male presented with a prolactin-producing pituitary adenoma with an atypical radiological appearance. The tumor was incidentally found by magnetic resonance imaging, which demonstrated a cystic tumor in the enlarged and partially empty sella turcica. Computed tomography revealed the tumor was surrounded by calcification with an egg-shell appearance. The serum prolactin level was 37 ng/ml. The operative finding was a calcified shell-containing cystic tumor. Immunohistochemical staining revealed prolactin-positive cells. The combination of the unusual calcification, and enlarged and partially empty sella was considered to be a sequela of spontaneous degeneration of the tumor.

Adult↗
PubMed1993

Preservation of cochlear nerve function in acoustic neurinoma surgery.

A total of 55 cases with unilateral acoustic neurinoma which were operated on by the lateral suboccipital approach was studied to elucidate factors which influence postoperative hearing acuity. We analyzed several factors: preoperative hearing level, tumour size, tumour consistency (cystic or solid), and anatomical location of the cochlear nerve. The size of the tumours ranged from 1.2 to 5.8 cm in diameter. Thirty of 55 cases (55%) preoperatively had remaining cochlear function. The smaller the size of tumour, the higher was the preoperative hearing level excepting those tumours with a diameter of 5 cm or greater, which had relatively good hearing and often contained large cysts. As to the consistency of the tumours, 41 were solid and 14 were cystic, where 19 (46%) and 11 (79%) cases had had preoperative hearing, respectively. Anatomical continuity of the cochlear nerve was maintained at surgery in 15 of 30 cases with preoperatively remaining hearing; cochlear function was preserved after surgery in 9 of the 15 cases. It was located counter-clockwise (caudally) to the facial nerve at an angle of 50 degrees on average when they were projected on the right side. The distance or interrelation between the two nerves had no bearing on postoperative hearing preservation. Postoperatively, hearing acuity was improved in 6 cases (20%) with a mean value of 5.6 dB, unchanged in 3 (10%), and deteriorated in 21 (70%) among the 30 cases with remaining preoperative-hearing. When the tumour was less than 2 cm or cystic, better hearing preservation was expected.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Posterior fossa subdural empyema in the term neonate.

A case of posterior fossa subdural empyema following neonatal meningitis is reported. Computerized tomography (CT) carried out on the 11th day after birth showed an obstructive hydrocephalus with diffuse cerebellar swelling. Ventricular drainage was carried out to control the hydrocephalus and antibiotics were given intravenously. A second CT scan taken on the 21st day after birth revealed a loculated subdural empyema in the retrocerebellar space. Serial CT scans showed a diminution in the size of the empyema.

Anti-Bacterial Agents↗
PubMed1987

Clinical study of brain retraction in different approaches and diseases.

Pressure of brain retraction was measured with a strain gauge spatula in 31 cases of 21 tumours and 10 aneurysms. They were operated on via different approaches: subfrontal (10 cases), interhemispheric (5), subtemporal (7) and suboccipital (9). The patients' age ranged from 11 to 74 years (average 50). The recorded data were averaged for every 5 minutes and divided into two groups: the first was data taken in the initial stage during the approach to the lesions, and the second were those taken during procedures at and around the lesion. Significant difference in the pressure among different approaches was found in the tumour group approached by the subtemporal route compared with other routes (p less than 0.005). The retraction pressures in the tumour cases were higher during the approach (31 +/- 15.5 torr) than during the main procedure (12 +/- 9.2 torr) (p less than 0.025). On the other hand, the pressures in the aneurysm cases were the reverse, being lower during the approach (22 +/- 15.2 torr) than during the main procedure (38 +/- 17.7 torr) (p less than 0.01). Early-stage operations for aneurysm required a higher retraction pressure than delayed operations.

Adolescent↗
PubMed1987

Monitoring retraction pressure on the brain. An experimental and clinical study.

The problem of minimizing tissue damage during brain retraction was studied both experimentally in dogs and clinically with the aid of newly designed strain-gauge retractor. The pressure required to obtain a specific exposure decreased gradually with time. The average time for a 50% reduction in retraction pressure was 6.6 minutes in the earlier trials of repeated retraction. The attenuation rate of retraction pressure gradually decreased when retraction of the same area was repeated. The lower the head position of the dog, the larger was the amplitude of brain retraction pressure. Clinical studies demonstrated that: 1) cerebrospinal fluid drainage was effective in decreasing the retraction pressure required; 2) use of multiple retractors reduced the pressure applied by each retractor; and 3) retraction pressure could be monitored when the strain-gauge retractors were applied to arteries and cranial nerves.

Adolescent↗
PubMed1986

Anterior cerebral artery reconstruction.

Anterior cerebral artery end-to-end, end-to-side, and side-to-side anastomoses and grafting procedures including bypass and interposition using segments of the posterior cerebral artery harvested from the same specimen were performed. The reconstruction procedures were accomplished experimentally with the A1 and A2 segments of the anterior cerebral artery, the recurrent artery of Heubner (RAH), and the orbitofrontal and frontopolar arteries in end-to-end or end-to-side anastomosis to the A1 segment. Side-to-side anastomoses between both A2 or A3 segments were completed without difficulty. We utilized the anatomical and experimental reconstruction data in the performance of three surgical procedures for aneurysms in this area. An A1 to A2 end-to-end anastomosis, an A2 to A2 end-to-side anastomosis, and an end-to-end anastomosis of the RAh were performed with no technical difficulties or complications. This study shows the feasibility of these microvascular reconstruction procedures in the anterobasal part of the interhemisphere, where cerebral aneurysms frequently develop.

Adult↗
PubMed1983

Intermittent versus continuous brain retraction. An experimental study.

Brain damage due to retraction was studied morphologically and physiologically in the dog brain. Two methods of retraction were compared using a retractor with a strain gauge: 1) continuous retraction; and 2) intermittent retraction. Total retraction time was 60 minutes for each method. Brain damage started to appear at a retraction force of 30 gm with continuous retraction, and increased in proportion to the force used. The power spectrum of the electrocorticogram showed full recovery after the release of retraction when the retraction force was less than 40 gm. With intermittent retraction, the damage was morphologically minimal with a retraction force of less than 50 gm, and recovery of the power spectrum of the electrocorticogram was prompt in comparison with continuous retraction. The results indicate the superiority of intermittent over continuous retraction.

Animals↗