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Biomedical subjects

Y Mayanagi

Publications and source records attributed to Y Mayanagi.

At least 37 records · Page 2Linked to original sources
PubMed1987

Three-dimensional digitizer (neuronavigator): new equipment for computed tomography-guided stereotaxic surgery.

A new device was invented as an adjunct for computed tomography (CT)-guided stereotaxic or open neurosurgery. It is composed of a multijoint three-dimensional digitizer (sensor arm) and a microcomputer, which indicates the place of the sensor arm tip on preoperative CT images. Computed tomography scan is performed preoperatively with three markers placed on the nasion and ears. At surgery, after fixing the patient's head and the sensor arm, sampling of the standard points was done to translate the position of the tip of the sensor arm onto the CT images displayed on a computer screen. In this way positional data from conventional preoperative CT scan can be directly transferred into the surgical field. This system has the unique feature of introducing CT-guided stereotaxis into conventional open neurosurgery.

Brain Neoplasms↗
PubMed1987

[Mechanism of deafferentation pain--experimental research using spinal root resection model].

In rats, autotomy of the digits following dorsal root resection has been observed by many researchers and is considered as an animal model of deafferentation pain. Using C5-Th 1 root resection model of rats, we investigated the role of the ventral roots and pain experience given before deafferentation in the development of autotomy. Male Sprague-Dawley rats of eight weeks old, weighing about 200 g, were used. Animals were divided into two major groups; dorsal root resection group and total (both ventral and dorsal) root resection group. Each group was further divided into several sub-groups, according to the use of formalin injection, before or after surgery, and to the side of formalin injection, the forearm of the affected (root resection) side or unaffected side or of both sides. In pre-injection groups, 0.1 ml of 5% formalin was given subcutaneously on the forearm one hour before surgery. In the postinjection groups, formalin was given within one hour after surgery. Dorsal root resection group without formalin injection was used as control. Under anesthesia with intraperitoneal injection of nembutal, left C 5-Th 1 dorsal root resection was performed by C 4-Th 1 laminectomy and left C5-Th 1 total root resection by opening of the corresponding vertebral foramen. After surgery, we checked neurological findings, systemic condition and local changes of all the extremities everyday during the first week and once a week thereafter for at least three months. In control groups, autotomy was not observed at all during the observation period of three months.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1987

Decreased dopamine level in the epileptic focus.

Catecholamine and serotonin in the focus tissues of 12 intractable epileptic patients who underwent surgery were analysed by high performance liquid chromatography with electrochemical detection, and it was found that dopamine contents in epileptic foci were clearly lower than in surrounding tissue in 7 of the 12 epileptics examined. In the other 5 patients, dopamine levels were much lower than in non-convulsive neuropathic patients.

Adolescent↗
PubMed1986

[A case of growth hormone-producing adenoma presenting as a non-functioning tumor at recurrence].

The authors report a case of recurrent pituitary adenoma, which changed its endocrinological function from GH producing to non-functioning. A 37-year-old woman was admitted to our hospital complaining of headaches, amenorrhea and acromegalic features. Skull X-rays showed marked ballooning of the sella turcica and mild thickening of the calvarium. X-rays of the hands and feet revealed moderate acromegalic changes. On pneumoventriculography, the tumor elevated the floor of the third ventricle. The serum GH level was 29.3 ng/ml, which did not respond to insulin induced hypoglycemia. Radical removal of the tumor was performed through a right frontal craniotomy. Histologically, it was diagnosed as a pituitary eosinophilic adenoma. Immunostains revealed the presence of many GH positive cells in the adenoma. Since the post-operative GH levels were still high (12-16 ng/ml), irradiation to the sellar region was carried out. The serum GH concentration gradually decreased to the normal level in one year after the irradiation. At that time no sellar tumor could be found on CT scans. The patient had been well for six years until she noticed hearing impairment of her right ear. She was re-admitted about seven years after the first admission because of cerebellar ataxia and hearing loss. CT scans revealed a recurrent tumor extending from the sellar region to the right cerebello-pontine angle. Serum GH levels on admission were within normal range (3-4 ng/ml). The tumor was partially removed by suboccipital craniectomy. Pathologically, the tumor was reported as a pituitary chromophobe adenoma. With immunostains, no GH positive cells could be found in the adenoma.(ABSTRACT TRUNCATED AT 250 WORDS)

Acromegaly↗
PubMed1984

Intracranial recording of short latency somatosensory evoked potentials in man: identification of origin of each component.

In normal subjects the short latency SEPs generally consisted of 3 positive waves (P9, P11, P14) and a succeeding negative wave (N20). To determine the origins of these waves we have made intracranial records from 17 patients, which suggest the following results. P9 originates in stimulated median nerve peripheral to the dorsal roots such as brachial plexus, P11 in the dorsal column of the cervical cord, P14 in the cuneate nucleus and medial lemniscal pathway, and N20 in the cerebral cortex. On the basis of intracranial and intraspinal records, the onset of P11 indicates the arrival of the afferent volley at the cord entry and the peak latency of P11 its arrival time at the C1-2 level dorsal column. The onset latency of P14 indicates the onset of postsynaptic events in cuneate nucleus neurons and the peak latency of P14 arrival at the midbrain. From the ventral surface of the brain-stem 3 positive waves (P'9, P'11, P'14) like the initial positive components of the scalp short latency SEPs (P9, P11, P14) were recorded. The amplitude of P'14 was large compared to that of P14. The peak latencies of P'14 recorded at the medulla and the pons were shorter than that of P14 by 0.7-0.8 msec and 0.2-0.5 msec, respectively. The peak latency of P'14 at the midbrain was almost the same as that of P14. By measuring the distance between the recording electrodes in the brain-stem and the peak latency difference of P'14, the fastest lemniscal conduction velocity was estimated as 56 m/sec.

Adult↗
PubMed1983

Extracranial-intracranial bypass to the proximal posterior cerebral artery and to the proximal middle cerebral artery for multiple occlusive cerebrovascular disease.

A 48-year-old man with a multiple occlusive cerebrovascular disease involving both the carotid and the vertebrobasilar systems is reported. Faced with noneffective conservative treatment, a surgical approach was carried out. As the patient had poorly developed posterior communicating arteries, two extracranial-intracranial bypasses were performed for both the carotid and the vertebrobasilar circulations; extracranial-intracranial bypasses with interposed saphenous vein grafts between the left external carotid artery and the proximal segment of the left middle cerebral artery, and between the right external carotid artery and the proximal segment of the right posterior cerebral artery. Advantages, precautions, and techniques of this kind of bypass procedure are discussed.

Brain Ischemia↗
PubMed1983

Elevated immunoreactive beta-endorphin level in ventricular fluid after analgesic electrical stimulation of posteromedial hypothalamus.

Immunoreactive beta-endorphin (beta-EP) in the ventricular fluid of six carcinomatous patients was measured using a specific radioimmunoassay. The subjects were undergoing a surgical procedure for relief of chronic intractable pain. This procedure involved the focal stimulation and coagulation of the posteromedial hypothalamus. Samples of ventricular fluid were collected before and after the stimulation and serially after the coagulation. Prior to stimulation, beta-EP-like immunoreactivity (beta-EP-LI) was below 200 pg/ml. In all of the six patients with pain relief, electrical stimulation led to a marked increase in immunoreactive beta-EP. In three patients beta-EP levels remained high after electrical coagulation for 6-24 hrs. These results suggest that beta-EP-like material, released into the ventricular fluid, may contribute to the initial pain blockade that results from stimulation and coagulation of the posteromedial hypothalamus.

Adult↗
PubMed1983

[The migration of cefotiam to cerebrospinal fluid].

The concentration of cefotiam (CTM), a newly synthesized cephem derivative antibiotic in serum and cerebrospinal fluid after single intravenous treatment was determined and its utility in the field of cerebral neurosurgery was studied. 1. One gram or 2 g of CTM was intravenously administered for 1 time to 10 patients admitted to our department. Dose dependency was observed in the progress of the mean serum concentration. There was no difference in the specific rate of constant, and the ratio of AUC between the group treated with 1 g and the one with 2 g was 1:1.9. The biological half-lives of the elimination phase for both dose levels were about 1.1 hours. 2. Disparity was recognized in the cerebrospinal fluid concentration in spite of the dose dependency. Although a case with comparatively high value of 1.37 micrograms/ml at 60 minutes after administration were seen in the 1 g treatment group, generally the migration concentration was low. Good cerebrospinal fluid concentration was attained in all of the cases in the 2 g treatment group, and the peak values ranged from 0.59 to 10.16 micrograms/ml. 3. The concentration ratio of cerebrospinal fluid to serum in the 2 g treatment group elevated till 360 minutes after administration, and the maximum values ranged from 15.8 to 89.8%. 4. The migration to the cerebrospinal fluid was faster in cases with slight inflammation than those without inflammation in the 2 g treatment group. 5. It was assumed that the prophylactic effect of CTM 2 g administration against staphylococci, streptococci and Klebsiella pneumoniae which are the major causative organisms can be expected in postoperative infection in the field of cerebral neurosurgery.

Adult↗
PubMed1983

[Extra-intracranial bypass and internal carotid artery ligation in one-stage operation for intracavernous and giant carotid aneurysm].

The combined one-stage operations, STA-MCA anastomosis and internal carotid artery (ICA) ligation (or trapping) were carried out in 11 cases (Age): 18-79 yrs, Av.: 45.8 yrs) of ICA aneurysms which were inaccessible for a direct operation because of their locations and sizes. First the STA-MCA anastomosis was performed under general anesthesia. Then the patient was awaken and thereafter under local anesthesia the ICA was temporarily clamped for 30 min. under induced hypotension to check whether any ischemic signs appeared. This was followed by proximal ICA ligation when no ischemic signs were observed. In all 11 cases, the anastomosis was patent. The aneurysms disappeared. Neither cerebral ischemia nor rebleeding from the aneurysms was seen during the long follow-up. The mean value of the bypass flow was 119 m/min which was twice as much as that in the cases of other occlusive cerebrovascular diseases and which was about one third of the blood flow of the ICA. Cerebral blood flow measurements through 133Xe inhalation method revealed that there was no difference in rCBF values between the operated and non-operated sides and that their values were within normal limits. The postoperative blood pressure was unchanged in 42% of our 11 cases, temporarily elevated and thereafter normalized in 33% and persistently elevated in 25%. Ophthalmodynamometry showed that the pressure of the central retinal artery decreased postoperatively in a degree of 5-10% in comparison to the non-operated side. No visual impairment was observed postoperatively (except case 3, see the text). These combined operations, STA-MCA anastomosis and ICA ligation were beneficial in preventing the potential postoperative cerebral ischemia. Intra-arterial pressure measurements of the STA and MCA suggested that the one-stage operations of these two procedures are better than the two-stage operations for the patency of the anastomosis because the pressure gradient between the donor and recipient vessels is increased (from 10.3 mmHg to 49.3 mmHg) by this technique. Temporary ICA clamp for 30 min. under induced hypotension in local anesthesia is useful to check whether the one-stage operations can be tolerated or not. EC/IC bypass with an interposed saphenous vein graft is a more beneficial surgical technique than a routine STA-MCA anastomosis, because an immediate and larger amount of bypass flow can be obtained.

Adult↗