A shared accretion instability for black holes and neutron stars.

Accretion disks around compact objects are expected to enter an unstable phase at high luminosity1. One instability may occur when the radiation pressure generated by accretion modifies the disk viscosity, resulting in the cyclic depletion and refilling of the inner disk on short timescales2. Such a scenario, however, has only been quantitatively verified for a single stellar-mass black hole3-5. Although there are hints of these cycles in a few isolated cases6-10, their apparent absence in the variable emission of most bright accreting neutron stars and black holes has been a continuing puzzle11. Here we report the presence of the same multiwavelength instability around an accreting neutron star. Moreover, we show that the variability across the electromagnetic spectrum-from radio to X-ray-of both black holes and neutron stars at high accretion rates can be explained consistently if the accretion disks are unstable, producing relativistic ejections during transitions that deplete or refill the inner disk. Such a new association allows us to identify the main physical components responsible for the fast multiwavelength variability of highly accreting compact objects.

A persistent ultraviolet outflow from an accreting neutron star binary transient.

All disc-accreting astrophysical objects produce powerful disc winds. In compact binaries containing neutron stars or black holes, accretion often takes place during violent outbursts. The main disc wind signatures during these eruptions are blue-shifted X-ray absorption lines, which are preferentially seen in disc-dominated 'soft states'1,2. By contrast, optical wind-formed lines have recently been detected in 'hard states', when a hot corona dominates the luminosity3. The relationship between these signatures is unknown, and no erupting system has as yet revealed wind-formed lines between the X-ray and optical bands, despite the many strong resonance transitions in this ultraviolet (UV) region4. Here we report that the transient neutron star binary Swift J1858.6-0814 exhibits wind-formed, blue-shifted absorption lines associated with C IV, N V and He II in time-resolved UV spectroscopy during a luminous hard state, which we interpret as a warm, moderately ionized outflow component in this state. Simultaneously observed optical lines also display transient blue-shifted absorption. Decomposing the UV data into constant and variable components, the blue-shifted absorption is associated with the former. This implies that the outflow is not associated with the luminous flares in the data. The joint presence of UV and optical wind features reveals a multi-phase and/or spatially stratified evaporative outflow from the outer disc5. This type of persistent mass loss across all accretion states has been predicted by radiation-hydrodynamic simulations6 and helps to explain the shorter-than-expected duration of outbursts7.

Ataxic hemiparesis associated with ipsilateral cerebellar syndrome caused by a paracentral gyrus lesion.

The authors report a case of ataxic hemiparesis and an ipsilateral cerebellar syndrome in relation to a glioblastoma of the paracentral gyrus region. The physiopathology of this clinical presentation caused by compression of the corticopontine tract is discussed.

Surgical treatment of a rare congenital anomaly of the vertebral artery: case report and review of the literature.

A case of an abnormal loop of the vertebral artery compressing both the cervicomedullary junction and the accessory nerve is reported. The embryological development of the vertebrobasilar system may explain this anatomical anomaly. The possibility of an abnormal location of the vertebral artery may complicate the lateral C1-C2 puncture for myelography. Only five similar cases have been reported previously, but none of them presented any clinical symptomatology, and surgical treatment was never required. The present patient was cured by microvascular decompression. The pathogenetic and surgical implications are discussed in light of the literature.

Perioperative lumbar injection of Ringer's lactate solution in chronic subdural hematomas: a series of 100 cases.

A series of 100 patients underwent surgical treatment for chronic subdural hematomas between 1979 and 1987. The procedure consisted of craniectomy with a 30-mm trephine, irrigation and drainage of the hematoma, laceration of the outer and inner membranes, and lumbar intrathecal injection of Ringer's lactate solution for immediate cerebral reexpansion (average injection, 130 ml). This technique gave the following results: 2% mortality, 2% moderate morbidity, and 96% recovery. The recovery of the patients was rapid, and good outcome was achieved in Grade 3 and Grade 4 cases (Markwalder's classification).

Microsurgical anatomy of the cisternal course of the perforating branches of the posterior communicating artery.

Both the perforating branches--especially the extracerebral segments--and the arachnoidal anatomy at the level of the posterior communicating artery were studied in 60 human brains previously fixed in formalin. The close relationships between this artery and the oculomotor nerve are described, and it is noted that each of them is enclosed in its own arachnoidal compartment, which in the case of the posterior communicating artery is to be distinguished from the interpeduncular cistern. The latter cistern was found to contain only the terminal segments of the posterior communicating artery. The hypothalamic branches were within the inner wall of the arachnoidal cistern surrounding the posterior communicating artery. The variations in diameter of this artery are explained by its embryological development and are not related to the number and the diameter of the perforators. The posterior communicating artery was absent at times. The surgical implications of such a variable anatomical arrangement are discussed in the light of the literature.

Anterior discectomy without fusion for treatment of cervical lateral soft disc extrusion: a follow-up of 120 cases.

One hundred and twenty patients with soft lateral disc herniation underwent surgery by anterior microsurgical discectomy and routine ablation of the posterior longitudinal ligament between 1976 and 1986. The study excluded patients with hard discs and soft disc extrusion with medullary symptoms. In our series 76.6% of patients were men. In 64% of the patients no causative factor was found. All of the patients presented with cervicobrachialgia; 53% also had a motor deficit. In 91.7% a single disc was involved. The last 40 cases were evaluated by computed tomography alone. In 51.5% an extruded disc was found. No permanent postoperative complication was encountered. All patients returned to their previous activities. Fifty patients underwent follow-up radiological evaluation at 1 and 5 years after the intervention and vertebral fusion was observed in 70% of these.

Surgical treatment of tentorial arteriovenous malformations draining into the subarachnoid space. Report of four cases.

Four patients with tentorial arteriovenous malformations (AVM's) were treated surgically. The operative findings in the first case suggested that clipping of the draining vein close to the AVM may result in complete cure. The three subsequent cases were treated with this technique. The clinical and radiological implications are discussed.

Perforating branches of the basilar bifurcation.

The perforating branches of the upper basilar artery and of the first (P1) segment of the posterior cerebral artery were studied in 50 fixed brains obtained from human cadavers. No vertical branches arose from the basilar bifurcation. The upper basilar artery gave rise to horizontal branches, which were studied with reference to their angle of origin. Perforating arteries arising from P1 segments were found in all specimens. Rare branches were found to come from the inferior and anterior surfaces of P1 segments. The anatomical patterns of these branches are discussed in the light of previous reports. Preoperative knowledge of some anatomical aspects (the position of the basilar apex, the angle between the right P1 and left P1 segments, and relationships to the dorsum sellae and the mammillary bodies) can help in the selection of a neurosurgical approach and may improve the operative results in the surgical treatment of basilar apex aneurysms.

Cylindromas of the base of the skull. Report of four cases.

Cylindromas are rarely encountered in the neurosurgical field. Four cases of this rare tumor are presented. Conventional and computerized tomography scanning were most useful in establishing the diagnosis; angiography did not provide any further information. Because these tumors are well demarcated from surrounding structures, even in cases of recurrence, surgery is the treatment of choice. Radiation therapy is useful in the postoperative management. Long survival times with multiple recurrences are the rule.

Intracranial malignant lymphoma. Report of 30 cases and review of the literature.

Although primary malignant lymphoma is a rare entity in the gamut of intracranial tumors, it is more frequently seen than the secondary intracranial spread of a primary extracranial lymphoma. In general, the occurrence of lymphomas seems to be provoked by immunosuppression, as with medication (predominantly after transplantation) or with immunodepressive disease such as acquired immunodeficiency syndrome (AIDS). The usual age of onset of this disease is 55 to 65 years; and the male:female patient distribution is roughly 2:1. Characteristically, computerized tomography (CT) scans of lymphomas show a mass which is often large with regular contours, moderate mass effect, and hyper- or isodensity with marked and often homogeneous enhancement. In the series of 30 patients reported, the locations of lesions, in order of decreasing frequency, were the frontocallosal and temporal regions, the basal ganglia, and the cerebellum. Multiple lesions were present in 15% of these cases (20% to 40% in the literature). The following features should raise the suspicion of intracranial lymphoma: mirror lesions of the basal ganglia, bilateral subependymal infiltration, and leptomeningeal involvement contiguous with an intracerebral mass. According to the literature, the angiographic finding typical of lymphoma is an avascular tumor. A blush or vascular encasement of the mass seems to be rare, and the present series was in accordance with other reports in this respect. Differential diagnostic consideration should include meningioma, glioblastoma, metastatic disease, and focal infectious lesions such as toxoplasmosis or multifocal progressive leukoencephalitis, particularly in immunodepressed subjects. Diagnosing lymphoma from CT scans offers the alternative of substituting stereotaxic biopsy and neuropathological diagnosis for the more aggressive open surgical approach, since radiation therapy and possibly chemotherapy usually prove to be the treatment of choice.

Association between an aneurysm of the anterior inferior cerebral artery and an arteriovenous malformation fed by the same artery.

An unusual case of distal aneurysm of the anterior inferior cerebellar artery (AICA) associated with a cerebellar arteriovenous malformation in a 35 year-old woman is reported. The clinical presentation was a subarachnoid hemorrhage, that is the sudden onset of headache while she was driving her car. In the following days the patient experienced a cerebellopontine angle syndrome: unsteadiness, tinnitus and hearing loss in her left ear, along with drop episodes. All symptoms disappeared in about a week. She consulted a neurosurgeon only a month later. On the day of admission in the Neurosurgical Department of Résidence du Parc Clinic her neurological status was normal. Neuroradiological investigations showed the association between the two distal AICA malformations. At surgery it was possible either to clip the aneurysm or to remove the AVM. The origin of the hemorrhage has not been clearly identified. The patient had an uneventful recovery and returned to her job three months later. The aneurysm was located on the same artery that supplied the AVM. This association is rare at the AICA level. The possible development of the aneurysm induced by increase in flow through the AVM is discussed in the light of Literature data.

Epidermoid cysts of the fourth ventricle.

The location of epidermoid cysts within the fourth ventricle is rare. The Authors present three cases operated on. The most frequent symptom was ataxia. Increased intracranial pressure and hydrocephalus were rare even when the tumors were large in size and filled up the fourth ventricle. Neuroradiological data are presented. Surgical removal was generally easy though the tumor invaded the cisterns and a true peritumoral capsule was found only in the lower part of the ventricular floor. The bursting of the cyst followed by continuous production of keratin with subsequent invasion of cisterns and foramina is suggested as a possible mechanism to explain the tumoral growing.

Hemangiopericytomas of the spinal canal. Report of four cases and review of literature.

The Authors report four cases of spinal hemangiopericytomas. The diagnosis has been ascertained by electron microscopy. Despite the malignant nature, the association of surgery and radiotherapy is interesting in that it prolongs the survival rate. Clinical, neuroradiological, microscopic and ultrastructural features of intraspinal hemangiopericytomas are evaluated in the light of the review of the relevant literature.

Modalities of origin of the middle cerebral artery. Incidence on the arrangement of the perforating branches.

In a series of 100 anatomical dissections on the basal brain arteries a case of real duplication at the middle cerebral artery level has been found. The importance of such a finding is discussed in the light of literature data. The knowledge of similar anatomical patterns is fundamental in the study of the lenticulostriate arteries arising from the sphenoidal segment of the middle cerebral artery. In fact the neurosurgeon must be familiar with all the possible variations of these perforators, given that the opening of the Sylvian fissure is by now an obligatory manoeuvre for the transcisternal access to the circle of Willis.

Transsphenoidal surgery for acromegaly--long-term results in 100 patients.

A series of 100 patients with acromegaly who were operated on using the transsphenoidal microsurgical approach is presented along with a review of the literature. Emphasis is placed on long-term follow-up to assess the value of the technique. The authors caution against early normalization of growth hormone as a criterion for biologic cure in that cases of late recurrence are presented. It is proposed that 5 ng/mL baseline growth hormone values with normal dynamic testing is the most reliable way to ascertain biologic cure. Using these criteria, a cure rate of 78% for enclosed and 33% for invasive adenomata was obtained. No long-term recurrence was seen in patients considered cured along these lines.

Prolactin secreting adenoma in 22 men.

The authors report on 22 men with a prolactin secreting adenoma. Clinical symptomatology included associated signs of tumoral compression with varying degrees of hypogonadism. Endocrinological evaluation disclosed hyperprolactinemia in all cases but one, and hypopituitarism in 10 of 22 cases. Of the 22 patients, 21 underwent transsphenoidal microsurgery (two of whom underwent a second procedure by the infrafrontal approach) and in one case surgery was performed by the infrafrontal route. Diagnosis was confirmed by immunocytochemical evaluation of tumoral tissue. Prolactin levels returned to normal in 32% of cases after operation and became normal after complementary bromocriptine therapy in 54.5% of cases. However, normal prolactin secretion was not consistently accompanied by a return to normal of gonadotropin regulation. In three patients radiotherapy was not effective. The latter treatment should be limited to the very rare cases of postoperative resistance to bromocriptine.

Primary cerebral neuroblastoma in an adult man.

Survey of the literature reveals 10 cases of cerebral neuroblastoma in adults. An additional case, confirmed by electron microscopy, is reported here. The patient had a voluminous supratentorial calcified intraventricular tumor with clinical signs dating back more than two years. Despite the size and cellular immaturity of the lesion, surgical removal of the tumor was apparently satisfactory on macroscopic grounds. Treatment also included postoperative radiotherapy of the brain and spinal cord. The present case is discussed in light of the scarce data from the literature.

Microsurgical management of tuberculum sellae meningiomas. Results in 28 consecutive cases.

A series of 28 cases of meningioma of the tuberculum sellae is reviewed. This tumor was most frequent in the fifth decade, with a clear predominance in women. Neurological and endocrine deficits were minimal, whereas ophthalmologic signs were always present. Visual deficits were bilateral in cases with more than a 1-year history. Osteoma of the tuberculum sellae was rare and had no correlation with tumor size. Angiography of the internal carotid artery was found useful in demonstrating vascular displacements and tumor blush. Computed tomography was the most reliable diagnostic tool. All patients underwent a unilateral pterional craniotomy using the operating Outside of patients with total blindness, improvement of visual acuity was the rule, even in cases of long-term duration. Best results were obtained in patients operated upon within 1 year of the onset of visual symptoms.

Extracerebral course of the perforating branches of the anterior communicating artery: microsurgical anatomical study.

Damage to the perforating branches arising from the anterior communicating artery, because of their blood supply to the septal nuclei and anterior hypothalamus, explains the memory impairment and the electrolyte disturbances that often follow the surgery of aneurysms located in this part of the circle of Willis. The microsurgical anatomy of these branches was studied on 60 fixed human brains, with special attention to their number, caliber, and vascular territory. The direction of the branches was evaluated, measuring the angle formed by them with the postcommunicating segment of the anterior cerebral artery. The variability of this anatomical region is discussed in light of the literature.