Coherency provides a method to evaluate model linearity. The characteristics of pressure wave transmission in the intracranial cavity were studied by coherency in 16 cats with hydrostatic pressure loading to assess the linearity of the system, which is an assumption for use of the transfer function. Linearity was observed in only the fundamental waves of the respiration-induced component and the cardiac-induced component of intracranial pressure oscillation, and in the second harmonic wave of the latter. Linearity at the other frequencies was close to zero. The pressure transfer system in the intracranial cavity was basically a non-linear system. As intracranial pressure rose, the increase in the pressure transfer efficiency was largest in the low-frequency domain and smallest in the high-frequency domain, indicating that the cerebral blood vessels are characterized by inferior transmission of high frequency due to increased intracranial pressure. In addition, the correlation between the coherencies of the cardiac-induced fundamental wave component and intracranial pressure, and between those of the cardiac-induced second harmonic wave component and intracranial pressure, showed that the slope of the straight line was greater between 45 and 70 mmHg than between 10 and 45 mmHg. This suggests that there is a break point, located between 45 and 70 mmHg, where the increase in the coherency values is accelerated, caused by an increase in the intracranial elastance, as well as an increase in the cerebrovascular compliance due to the reduced vascular transmural pressure.
Histological changes in and around the arterial walls of rats were investigated following topical application of aneurysmal wrapping and coating materials, including a fibrin glue, a cyanoacrylate glue (Biobond), and cotton fibers (Bemsheet). Bilateral common carotid arteries were exposed using sterile techniques, and one of the test materials was applied to the right artery. The left artery was used as the control. Changes in arterial histology were evaluated at 2 weeks, 1 month, 2 months, and 3 months after surgery. The fibrin glue was surrounded by intense inflammation at 2 weeks after surgery. Both the fibrin glue and inflammation had disappeared at 2 months, but the glue had induced mild inflammation in the adventitia. Biobond caused chronic inflammation, necrosis of the media, and thickening of the arterial wall due to fibrosis in both the media and adventitia. Bemsheet produced chronic inflammation, progressive fibrosis, and granuloma. Connective tissue increased in the adventitia, but no major changes were observed in the media. The Bemsheet fibers remained unchanged, and adhered to the arterial wall. Although arterial stenoses were not observed in the present study, the results suggest that cyanoacrylate glue can cause the arterial occlusive lesions observed following aneurysm surgery.
Serial magnetic resonance (MR) images taken after acoustic neuroma surgery were analyzed to evaluate the pattern and timing of postoperative contrast enhancement in 22 patients who underwent acoustic neuroma removal via the suboccipital transmeatal approach. The opened internal auditory canal (IAC) was covered with a muscle piece in nine patients and with fibrin glue in 13. A total of 56 MR imaging examinations were obtained between days 1 and 930 after surgery. MR imaging showed linear enhancement at the IAC within the first 2 days after surgery, and revealed nodular enhancement on day 3 or later in patients with a muscle piece. MR imaging tended to show linear enhancement at the IAC, irrespective of the timing of the examination in the patients with fibrin glue. Postoperative MR imaging on day 3 or later showed the incidence of nodular enhancement in patients with muscle was significantly higher than in patients with fibrin glue. The results illustrate the difficulty in differentiating nodular enhancement of a muscle piece from tumor by a single postoperative MR imaging study. Therefore, fibrin glue is generally advocated as a packing material of the IAC because it rarely shows masslike enhancement on postoperative MR imaging. When a muscle piece is used in patients at high risk for postoperative cerebrospinal fluid leaks, MR imaging should be obtained within the first 2 days after surgery, since benign enhancement of muscle will not occur and obscure the precise extent of tumor resection.
A 4-year-old boy presented with a transorbital-transpetrosal penetrating head injury after a butter knife had penetrated the left orbit. The knife tip reached the posterior fossa after penetrating the petrous bone. Wide craniotomy and the pterional, subtemporal, and lateral suboccipital approaches were performed for safe removal of the object. The patient was discharged with left-sided blindness, complete left ophthalmoplegia, and hypesthesia of the left face. Early angiography is recommended to identify vascular injury which could result in fatal intracranial hemorrhage.
A 60-year-old male with recurrent syncopal attacks presented with orthostatic hypotension on the head-up tilt test. Angiography also showed severe stenosis of the bilateral extracranial carotid arteries. He underwent two-staged bilateral carotid endarterectomy. After the operations, the orthostatic hypotension resolved and the syncopal attacks have disappeared completely. Orthostatic hypotension in this patient was due to vasodepressor-type carotid sinus syndrome caused by compression of the carotid baroreceptors by atherosclerotic plaques.
A 27-year-old male presented with a rare association of a ruptured orbitofrontal artery aneurysm and a dural arteriovenous malformation (DAVM) fed by both ethmoidal arteries, manifestation as severe headache, nausea, and vomiting. Computed tomography revealed a hematoma within the right frontal lobe and diffuse subarachnoid hemorrhage. The aneurysm was clipped successfully and the hematoma was evacuated. After an uneventful postoperative course, the patient was referred for gamma knife radiosurgery to treat the DAVM. In this case, the DAVM was asymptomatic and pathogenetically unrelated to the aneurysm, which demanded urgent treatment.
A 77-year-old female presented with a rare intrameatal aneurysm manifesting as sudden onset of headache, hearing loss, tinnitus, and vertigo associated with subarachnoid hemorrhage. Meatal loop trapping was performed. After surgery, the patient''s functions recovered almost completely, probably because of the preservation of the 7th and 8th cranial nerves and the presence of effective collaterals in the area supplied by the anterior inferior cerebellar artery.
A 70-year-old male presented with pituitary metastasis from transitional cell carcinoma of the urinary bladder manifesting as sudden headache, transient unconsciousness, and visual disturbance mimicking apoplexy of pituitary adenoma. Computed tomography showed a suprasellar tumor with intratumoral and intraventricular hemorrhage. Magnetic resonance imaging demonstrated an intra and suprasellar mass lesion mimicking pituitary adenoma. Diabetes insipidus developed soon after. The tumor was subtotally removed. Histological examination revealed transitional cell carcinoma. An intratumoral hemorrhage may be associated with a pituitary metastasis if the patient presents with symptoms such as pituitary apoplexy.
A 17-year-old male presented with paroxysmal kinesigenic choreoathetosis (PKC) associated with frontotemporal arachnoid cyst. Xenon-133 single photon emission computed tomography detected a slight but equivocal decrease in regional cerebral blood flow in the vicinity of basal ganglia associated with the PKC episodes. PKC continued after surgical removal of the cyst but was well controlled by oral administration of carbamazepine. Whether the pathogenesis of symptomatic PKC was associated with the cortical lesion could not be determined in the present case.
A 61-year-old female presented with headache, malaise, and left oculomotor nerve paralysis. Computed tomography (CT) demonstrated a diffuse pituitary mass and enlarged pituitary stalk with homogeneous contrast enhancement. Her symptoms gradually resolved without treatment. Gallium-67 scintigraphy showed abnormal uptake in the pituitary lesion. Serial CT every 2 weeks after admission showed homogeneous contrast enhancement and shrinking of the pituitary mass to a normal size 12 weeks after the onset. The final diagnosis was lymphocytic adenohypophysitis without biopsy. Recurrence has not been observed for 8 years after discharge. The patient did not need hormone replacement therapy. Histological examination is not always necessary to diagnose probable lymphocytic adenohypophysitis with the characteristic feature of rapid onset, abnormal gallium-67 uptake in the lesion, and resolution of symptoms in the acute stage with shrinking of the lesion on neuroimaging.