Reentrant spin-glass transition in a dilute magnet.

We perform a large-scale Monte Carlo simulation of a dilute classical Heisenberg model with ferromagnetic nearest neighbor and antiferromagnetic next-nearest neighbor interactions. We found that the model reproduces a reentrant spin-glass transition. That is, as the temperature is decreased, the magnetization increases rapidly below a certain temperature, reaches a maximum value, and then disappears at some lower temperature. The low temperature phase was suggested to be a spin-glass phase that is characterized by ferromagnetic clusters.

Surgical strategy for cavernous angioma in hypothalamus.

A very rare case of cavernous angioma in the hypothalamus is presented. The patient was successfully treated by total excision of the haematoma and angioma, and there was no regrowth of the lesion on follow-up MRI. Complete excision of the angioma is the recommended surgical strategy even for patients with deep-seated lesions.

Injury and repair of the soleus muscle after electrical stimulation of the sciatic nerve in the rat.

To study injury and subsequent changes in skeletal muscles, the rat sciatic nerve was electrically stimulated at 50 Hz and muscle contraction was induced for 30 min. Muscle damage was classified into five types (hypercontraction, hyperstretching, Z band disorders, misalignment of myofilament and regions of scarce myofilaments) by electron microscopy and quantified by ultrastructural assessment. After electrical nerve stimulation, the percentages of the injured areas of the soleus muscle were 18.8 +/- 15.8% (mean +/- SD) at 0 h, 9.7 +/- 1.0% at 6 h, 22.0 +/- 23.6% at 12 h, 13.1 +/- 3.2% at 24 h, 4.9 +/- 6.0% at 3 days and 0.5 +/- 0.4% at 7 days. At 0 h, the vast majority of ultrastructural alterations were sarcomere hypercontraction. At 6 h, hypercontraction was not recognizable and sarcomere hyperstretching and Z band disarrangement constituted the major findings. At 12 h, when the injury reached its maximum, myofilament disorganization and hyperstretching were predominant. At 24 h or afterwards, the injury began to decrease and recovered to almost normal conditions by 7 days. There were very few necrotic muscle fibers in all specimens. It is considered that the muscle lesions in the present study were reversible, and recovered through changes in various types of sarcomere alterations. Z band streaming and free ribosomes were frequently found at 12 and 24 h, which may indicate repair processes rather than newly formed lesions.

Microvascular decompression for cochlear symptoms.

OBJECT: The object of this study was to evaluate the efficacy of a new neurovascular decompression technique in relieving symptoms of cochlear nerve dysfunction. METHODS: Nineteen patients with slowly progressive hearing loss, low-frequency fluctuating hearing loss, and high-pitched tinnitus due to neurovascular compression (NVC) of the eighth cranial nerve in a triangular space between the seventh and eighth cranial nerves (the VII-VIII triangle) of the cerebellopontine angle (CPA) were treated using a new technique for microvascular decompression that was developed by anatomical study in 24 cadaver specimens of the CPA. In 12 of 19 patients the anterior inferior cerebellar artery (AICA) was observed to cause compression in the VII-VIII triangle and this vessel was easily mobilized medially for placement of a silicone sponge or Teflon cushion between the compressing artery and nerve. Postoperatively, hearing loss of 20 dB or more that was present in 11 of the 19 patients with NVC improved by more than 5 dB in seven (64%), including the patient with the most severe hearing loss. Of 18 patients presenting with tinnitus preoperatively, eight (44%) had no tinnitus and an additional nine (for a total of 94%) had good improvement in tinnitus after surgery and at long-term follow up. CONCLUSIONS: The microvascular decompression technique described is highly successful in treating symptoms due to direct or indirect compression of the cochlear nerve, with minimal risk of complications. Recordings of auditory brainstem responses confirmed the clinical diagnosis of NVC of the eighth cranial nerve and correlated with clinical results after microvascular decompression of the cochlear nerve.

Time-resolved electron spin resonance of gallium and germanium porphyrins in the excited triplet state.

Gallium and germanium porphyrin complexes in the lowest excited triplet (T1) state have been studied by time-resolved electron spin resonance (TRESR). It is found that for Ge(TPP)(OH)2 (TPP = dianion of tetraphenylporphyrin) intersystem crossing (ISC) from the lowest excited singlet (S1) state to the T1x and T1y sublevels is faster than that to the T1z sublevel (T1x, T1y, and T1z are sublevels of the T1 state), while the ISC of ZnTPP and Ga(TPP)(OH) is selective to the T1z sublevel. This is interpreted by a weak interaction between the dpi orbital of germanium and LUMO (eg) of the porphyrin ligand, resulting in small spin-orbit coupling (SOC). The interpretation is supported by molecular orbital calculations. The ISC of Ge(OEP)(OH)2 (OEP = dianion of octaethylporphyrin) and Ge(Pc)(OH)2 (Pc = dianion of tetra-tert-butylphthalocyanine) is found to be selective to the T1z sublevel in contrast to Ge(TPP)(OH)2. This dependence on the porphyrin ligand is reasonably explained by a difference between the 3(a(1u)eg) (the OEP and Pc complexes) and 3(a(2u)eg) (the TPP complex) configurations. This is the first observation of a difference in selective ISC between the 3(a(1u)eg) and 3(a(2u)eg) configurations. The TRESR spectrum of Ge(TPP)Br2 is different from those of Ge(TPP)Cl2 and Ge(TPP)(OH)2, and is interpreted by SOC between the T1 and T2 states. From ESR parameters the square of the coefficient of the eg orbital on bromine is evaluated as 0.018 in the T1 state.

[Diagnosis and treatment of nontraumatic dissecting aneurysm in the middle cerebral artery].

Two cases of nontraumatic dissecting aneurysm of the middle cerebral artery (MCA) are reported. A 59-year-old woman presented with subarachnoid hemorrhage, mainly in the right sylvian fissure. On admission, the right carotid angiogram revealed a dissecting aneurysm with a double lumen extending from segment M1 to M2 of the right MCA, and an unruptured saccular aneurysm in the right internal carotid artery. Emergency surgery revealed a discolored protrusion of the arterial wall in the right MCA, which was thought to be the cause of her subarachnoid hemorrhage. The protrusion of the arterial wall was clipped and coated with Bemsheet soaked in Biobond. However, disturbance of consciousness persisted and she died of paralytic ileus two months after the operation. The other patient was a hypertensive 33-year-old woman with right hemiparesis and motor dysphasia. CT scans obtained on the day of admission showed no abnormalities. She was treated conservatively with clinical improvement, but CT scans obtained 3 days after the ictus revealed an infarction deep in the left frontal lobe. A left carotid angiogram was made 4 days after ictus and demonstrated severe stenosis of the proximal segment of the left MCA with poor filling of its superior trunk. Despite improvement of her hemiparesis, CT scans obtained 3 weeks after the ictus showed hemorrhagic infarction in the left frontal lobe. Repeat left carotid angiogram revealed a double lumen in the C1 and M1 portions with improvement of the previous severe stenosis of the M1. The 23 reported cases of DA in the MCA with our cases are reviewed and their neuroradiological and clinical features are discussed.

Vertebral artery dissection not detected by initial angiography--case report.

A 57-year-old male presented with subarachnoid hemorrhage caused by vertebral artery dissection. The first cerebral angiogram on the day of ictus found minimal caliber change with lower contrast density at the V4 segment, but repeat angiography showed typical segmental narrowing of the artery on the 14th day. Repeat angiography with magnetic resonance imaging in the subacute stage would be useful to identify the cause of "angiogram-negative" subarachnoid hemorrhage.

Sphenoethmoidal mucoceles with intracranial extension--three case reports.

Three unusual cases of sphenoethmoidal mucoceles with rare intracranial extension are reported. A 64-year-old female presented with a 7-month history of right visual disturbance. Computed tomography (CT) and magnetic resonance (MR) imaging demonstrated a huge mass in the right middle fossa. She underwent right frontotemporal craniotomy. Postoperatively, her proptosis and cranial nerve dysfunction had improved markedly. A 53-year-old female complained of headache, nausea, and dizziness. CT and MR imaging revealed a cystic mass filling the right sphenoid sinus. The cystic lesion was evacuated through the transnasal approach. She was doing well postoperatively and has been asymptomatic. A 39-year-old male complained of headache, vomiting, and right visual disturbance. CT and MR imaging demonstrated a homogeneous mass occupying the sphenoid sinus. Sphenoidotomy exposed the cyst extending superiorly into the anterior cranial fossa. He recovered from the visual disturbances and has been asymptomatic since. MR imaging provides confirmation of the diagnosis of sphenoethmoidal mucocele and is important for preoperative evaluation.

Surgical modulation of the natural course of collateral circulation in chronic ischemic patients.

The purpose of this study was to evaluate hemodynamic compromise in terms of baseline CBF and CRC in patients with chronic cerebral occlusive lesions and its modulation by a superficial temporal artery to middle cerebral artery (STA-MCA) anastomosis. The study subjects were 10 healthy volunteers and 49 chronic ischemic patients with stenosis or occlusion of the internal carotid artery (ICA) or middle cerebral artery (MCA). The hemodynamics were measured using stable xenon enhanced computed tomographic CBF measurement with the acetazolamide challenge. The compromised hemodynamics in patients with chronic steno-occlusive lesions did not improve during their natural course after two months. STA-MCA bypass modulated hemodynamic compromise in the ischemic patients. We recommend STA-MCA bypass for patients with reduced CRC, regardless of whether baseline CBF is reduced or normal. Hemodynamic classification using a combination of baseline CBF values and CRC values is useful for evaluating cerebral hemodynamics and for choosing the best treatment for cerebral ischemia with occlusive lesions.

Pulmonary embolism after cerebral angiography--three case reports.

Three patients developed acute pulmonary embolism after cerebral angiography. The diagnoses were based on the clinical symptoms and echocardiography, chest roentgenography, blood gas analysis, and pulmonary perfusion scans after intravenous injection of 5 mCi of technetium-99m-labeled human albumin macroaggregates. Two of the three patients achieved clinical improvement, but one patient with severe embolization and circulatory deterioration died in spite of anticoagulation therapy. Recognition of the potential risk of pulmonary embolism after angiography and active prophylaxis are most important in preventing this complication.

Noninvasive detection of intracranial vascular lesions by recording blood flow sounds.

BACKGROUND AND PURPOSE: Transorbital blood flow sound recordings have the potential to be used for noninvasive detection of cerebral aneurysms and arteriovenous malformations. We describe our system and experience in detecting intracranial cerebrovascular disease. METHODS: We investigated the noninvasive detection of intracranial vascular lesions by recording and analyzing the intracranial blood flow sounds. A new small transducer was placed on the unilateral eyelid to record the intracranial blood flow sounds, which were amplified and converted to digital data at a sampling frequency of 2000 Hz to provide a spectral analysis. RESULTS: No spectral peaks were recorded in 30 healthy adults. Sharp peaks were recorded in 12 of 15 patients with unclipped aneurysms, and broad peaks were recorded in two patients with vasospasm after aneurysmal clipping and in all patients with severe intracranial internal carotid artery stenosis. CONCLUSIONS: This noninvasive technique has the potential to be very useful in the detection of intracranial cerebrovascular disease, including aneurysm and arterial stenosis, and could be used in mass screening examinations.

[Radiation-induced cerebrovasculopathy: a case report and review of the literature].

We reported a case of a patient who suffered from a cerebrovasculopathy after irradiation therapy for astrocytoma located at the left temporal lobe. An eleven year-old boy who presented himself with headache and vomiting as his chief complaints received partial removal of a tumor. Histological diagnosis of the tumor was astrocytoma (grade II). His preoperative cerebral angiograms showed mass sign solely, without stenosis or occlusion of the cerebral vessel. Postoperatively, he was treated with irradiation therapy involving the whole brain with a total of 30 Gy, and gamma knife therapy. Six months after irradiation, he started suffering from frequent cerebral ischemic attacks, but there was no regrowth of the tumor visible on CT scans. Cerebral angiograms were made again, and revealed multifocal stenoses in the bilateral internal carotid arteries, middle cerebral arteries, and the anterior cerebral artery. His symptoms did not improve after conservative treatment with steroids, calcium antagonist, or low molecular weight dextran. Although he received a superficial temporal artery-middle cerebral artery (STA-MCA) anastomoses bilaterally, multiple cerebral infarctions appeared. Although irradiation therapy is acceptable in patients with brain tumor, a cerebrovasculopathy after irradiation should be considered as one of the most important complications, and the risk incurred by irradiation therapy should lead to more careful consideration and caution when treating intracranial brain tumors, especially in children. From our experience, the usefulness of bypass surgery for radiation-induced cerebrovasculopathy is still controversial.

[A case of cough headache with Chiari malformation (type I)].

A 38-year-old woman complained for about 5 years of attacks of headache elicited by coughing, sneezing, and laughing. These attacks became more frequent and more severe. Physical examination showed a short and broad neck. Neurological examination revealed no abnormality. Magnetic resonance imaging demonstrated the Chiari malformation (type I) and the cerebral venous angioma in left frontal white matter. A posterior decompression by suboccipital craniectomy with C1 laminectomy was performed. The headache completely disappeared. Before and after the operation, we measured the intracranial subdural pressure by a small pressure transducer. The raised cranial pressure by the Valsalva's maneuver prolonged for more than one minute. Postoperatively, the raised cranial pressure by the Valsalva's maneuver decreased rapidly. We consider that the cough headache of this patient was associated with a valve-like blockage by the Chiari malformation (type I) at the foramen magunum, resulting in cranio-spinal pressure dissociation by interference with downward pulsation. We believe that there was no correlation between the cough headache and the cerebral venous angioma.

Abnormal continuous flow in giant intracranial aneurysm detected by transcranial Doppler sonography--case report.

Transcranial Doppler sonography demonstrated a huge, non-thrombosed intracranial aneurysm in a 62-year-old male preoperatively as abnormal continuous flow, which disappeared after aneurysmal neck clipping. Transcranial Doppler sonography is very useful to assess hemodynamics in the parent artery and the dome of the aneurysm.

Direct surgery for giant aneurysm exhibiting progressive enlargement after intraaneurysmal balloon embolization.

A case of giant intracranial carotid artery aneurysm exhibiting progressive enlargement after incomplete intraaneurysmal balloon embolization is presented. The patient was successfully treated by the trapping and decompression of the aneurysm with a superficial temporal artery-middle cerebral artery anastomosis. The thrombus surrounding the intraluminal balloons was very soft and poorly organized. Either direct surgery with extracranial-intracranial arterial bypass or complete intravascular surgery should be performed for giant aneurysms when direct clipping is impossible.

[A study of ionized calcium in the whole blood of patients with subarachnoid hemorrhage].

In 14 normal volunteers and 22 consecutive patients with subarachnoid hemorrhage (SAH) due to a ruptured cerebral aneurysm, ionized calcium (Ca2+) concentrations in whole blood were measured using an automatic calcium analyzer. The values were corrected against pH 7.4. The relationships between the Ca2+ concentration and the following aspects were studied: neurological grading by Hunt and Kosnik, grade of SAH on computed tomography scan by Fisher's definition, and the presence of vasospasm. Clinical vasospasm was recognized in eight cases. The averaged Ca2+ value of the control group was 1.23 +/- 0.02 mmol/l. In patients with a poor neurological grade or severe SAH, the Ca2+ level was apt to be lower than that of the control group. In patients with vasospasm, the values of Ca2+ were significantly decreased, especially between 8 and 14 days after SAH, compared with those patients without vasospasm and the control group (p less than 0.05). These results indicate that measurement of Ca2+ concentration in whole blood may give a useful clue to treatment of vasospasm by calcium antagonist and that it may also provide a possible indicator as to the time of vasospasm in patients with severe SAH. However, it is very difficult to conclude whether decreased level of Ca2+ in patients with vasospasm is caused by the vasospasm itself.

True posterior communicating artery aneurysm.

Two rare cases of true posterior communicating artery aneurysm are reported. One case was a saccular aneurysm, which was successfully clipped. The other was a case of fusiform trapped aneurysm, and hemiparesis and oculomotor palsy appeared transiently after surgery. In general, this type of aneurysm is included in the category of internal carotid-posterior communicating aneurysm, although some special considerations are necessary in surgical treatment.

Changes in brain stem blood flow under various grades of brain stem ischemia.

This report describes a study of brain stem blood flow (BBF) change under various grades of brain stem ischemia in a new experimental rat model. The main damage was caused by occlusion of the median and paramedian perforating arteries of the basilar artery. In this model, hyperperfusion was generally observed in cases of mild or moderate ischemia within 1 hr after recirculation and lasted for approximately 1 hr. During hyperperfusion, BBF increased to over 60 ml/100 g brain/min and was significantly greater than basal values (p less than 0.01). The fact that hyperperfusion was unobserved in some cases might be due to the degree of damage to the medulla oblongata. Hypoperfusion or lack of reflow phenomena was also followed by severe ischemia with remarkable hypotension. It is fairly clear from our results that the pattern of postischemic hyperperfusion is responsible for decreased oxygen availability in the brain stem and dysfunction of autoregulation. Acetazolamide reactivity was disturbed and had an inverse response during hyperperfusion. Such phenomena can be explained by paralytically dilated vessels due to ischemia. If BBF falls below a critical level, as we have seen, postischemic hyperperfusion may be induced with dysfunction of autoregulation and inverse acetazolamide reactivity due to vasoparalysis in the brain stem.