Alberto Romano

Microsurgical Anatomic Features and Nomenclature of the Paraclinoid Region

OBJECTIVE We describe the detailed microsurgical anatomic features of the clinoid (C5) segment of the internal carotid artery (ICA) and surrounding structures, clarify the anatomic relationships of structures in this region, and emphasize the clinical relevance of these observations. Furthermore, because the nomenclature of the paraclinoid region is confusing and lacks standardization, this report provides a glossary of terms that are commonly used to descibe the anatomic features of the paraclinoid region. METHODS The region surrounding the anterior clinoid process was observed in 70 specimens from 35 formalin-fixed cadaveric heads. Detailed microanatomic dissections were performed in 10 specimens. Histological sections of this region were obtained from the formalin-fixed cadaveric specimens. RESULTS The clinoid segment of the ICA is the portion that abuts the clinoid process. This portion of the ICA can be directly observed only after removal of the clinoid process. The dura of the cavernous sinus roof separates to enclose the clinoid process. The clinoid segment of the ICA exists only where this separation of dural layers is present. Because the clinoid process does not completely enclose the ICA in most cases, the clinoid segment is shaped more like a wedge than a cylinder. The outer layer of the dura (dura propria) is a thick membrane that fuses with the adventitia of the ICA to form a competent ring that separates the intradural ICA from the extradural ICA. The thin inner membranous layer of the dura loosely surrounds the ICA throughout the entire length of its clinoid segment. The most proximal aspect of this membrane defines the proximal dural ring. The proximal ring is incompetent and admits a variable number of veins from the cavernous plexus that accompany the ICA throughout its clinoid segment. CONCLUSION The narrow space between the inner dural layer and the clinoid ICA is continuous with the cavernous sinus via an incompetent proximal dural ring. This space between the clinoid ICA and the inner dural layer contains a variable number of veins that directly communicate with the cavernous plexus. Given the inconstancy of the venous plexus surrounding the clinoid ICA, we think that categorical labeling of the clinoid ICA as intracavernous or extracavernous cannot be justified.

Endothelin B Receptor Antagonists Attenuate Subarachnoid Hemorrhage–Induced Cerebral Vasospasm

BACKGROUND AND PURPOSE While it has been widely reported that the vasospasm following subarachnoid hemorrhage (SAH) is prevented/reversed by endothelin (ET) receptor antagonists selective for the ET(A) receptor and by nonselective ET receptor antagonists, ie, antagonists of both the ET(A) and ET(B) receptors, there are no reports on the possible attenuation of the spasm by selective ET(B) receptor antagonists. The purpose of this study was to investigate whether (1) ET(B) receptor antagonists prevent and reverse SAH-induced spasm and (2) attenuation of the spasm results from blockade of smooth muscle ET(B) (ET(B2)) receptor-mediated constriction and/or endothelial ET(B) (ET(B1)) receptor-mediated ET-1-induced ET-1 release. METHODS SAH-induced spasm of the rabbit basilar artery was induced with the use of a double hemorrhage model. In vivo effects of agents on the spasm were determined by angiography after their intracisternal infusion (10 microL/h) by mini osmotic pump. In situ effects of agents on the spasm were determined by direct measurement of vessel diameter after their suffusion in a cranial window. RESULTS SAH constricted the basilar artery by 30%. Intracisternal infusion with 10 micromol/L BQ788, an ET(B1/B2) receptor antagonist, reduced the spasm to 10%. To investigate whether BQ788 prevented the spasm by blockade of ET(B1) receptor-mediated ET-1-induced ET-1 release, as opposed to ET(B2) receptor-mediated constriction, we tested whether ET(B1) receptor blockade also prevented the spasm. Indeed, intracisternal infusion with 10 micromol/L RES-701-1, a selective ET(B1) receptor antagonist, reduced the spasm to 10%. Similarly, in situ superfusion with 1 micromol/L BQ788 reversed the spasm by 40%, and 1 micromol/L RES-701-1 reversed the spasm by 50%. However, both BQ788 and RES-701-1 enhanced by 40% to 50% the 3 nmol/L ET-1-induced constriction elicited in spastic vessels previously relaxed with 0.1 mmol/L phosphoramidon, an ET-converting enzyme inhibitor. CONCLUSIONS These results demonstrate that ET(B) receptor antagonists prevent and reverse SAH-induced cerebral vasospasm in an animal model. The likely mechanism underlying the attenuation of the spasm is blockade of ET(B1) receptor-mediated ET-1-induced ET-1 release of newly synthesized ET-1. These studies provide rationale for the therapeutic use of ET(B1) receptor antagonists to relieve the vasospasm following SAH, as well as other pathophysiological conditions involving possible ET-1-induced ET-1 release.

Microsurgical Anatomic Features of the Olfactory Nerve: Relevance to Olfaction Preservation in the Pterional Approach

OBJECTIVE: The pterional approach represents the standard approach for most lesions of the anterior and middle cranial fossa. It requires some degree of frontal lobe retraction, which may result in temporary or permanent damage of olfaction because of nerve avulsion or mechanical compression. The purpose of this study, based on microanatomic dissection of human cadaveric specimens, was to review the microsurgical anatomic features of the nerve and suggest operative nuances that may contribute to reducing the rate of postoperative olfactory dysfunction. METHODS: Twenty olfactory nerves and tracts were examined in 10 human cadaveric heads obtained from three fresh and seven formalin-fixed adult cadavers. A standard pterional craniotomy was performed. The olfactory nerve was dissected from its arachnoidal envelopes and then mobilized for an average length of 30 mm (range, 25–35 mm). RESULTS: The possible retraction of the frontal lobe was 10 to 15 mm. More retraction invariably resulted in nerve disruption. CONCLUSION: The standard sylvian and basal cistern opening may be insufficient to guarantee preservation of olfactory function. Early identification and arachnoidal dissection of the nerve may reduce the rate of olfaction compromise. The opening of the subarachnoidal space should be performed in a proximal-to-distal manner to allow early visualization of the olfactory bulb and its dissection. The arachnoidal dissection should be performed with sharp instruments, avoiding any traction on the posterior portion of the olfactory tract. Any direct retractor compression should also be avoided to spare the microvasculature lying on the dorsal surface of the nerve.

Eyelid approach to the anterior cranial base

Skull base approaches play a fundamental role in modern neurosurgery by reducing surgical morbidity. Increasing experience has allowed surgeons to perform minimally invasive approaches without straying from the premises of skull base surgery. The eyelid approach has evolved from the orbitopterional osteotomy into a more effective and targeted approach to disease of the anterior cranial fossa. In this technique, after an incision is made on the supratarsal fold, the orbicularis oculi muscle is incised, and a myocutaneous flap composed of the elements of the anterior lamella is elevated. Subperiosteal dissection is used to expose the superior and lateral walls of the orbit, the superior and lateral orbital rim, and the frontosphenoidal suture. A MacCarty bur hole is drilled, and a frontal osteotomy is fashioned medial to the supraorbital notch and extending through the orbital roof back toward the orbital half of the MacCarty bur hole, exposing the frontobasal brain. A conventional microsurgical technique is used to treat tumors and aneurysms of the anterior cranial fossa under the operative microscope. Five patients were treated for unruptured aneurysms of the anterior circulation (3 anterior communicating artery aneurysms, 1 ophthalmic artery aneurysm, and 1 posterior communicating artery aneurysm) using the eyelid approach. The mean aneurysm size was 5 mm, and all aneurysms were approached from the right side. Three tumors in the anterior fossa (2 suprasellar pituitary adenomas and 1 craniopharyngioma) were also excised using this approach. There was no surgical morbidity. Three months after surgery all patients presented excellent cosmetic results. The eyelid approach may be considered as an effective, cosmetically beneficial, and minimally invasive skull base approach to selected aneurysms and tumors of the anterior circulation.

Expanding the boundaries of the transsphenoidal approach: a microanatomic study.

The anatomic features of a transsphenoidal approach are reviewed, focusing on the microsurgical anatomy of parasellar structures. Pertinent microsurgical anatomy is described in sufficient detail for the neurosurgeon to successfully extend a standard transsphenoidal approach for treatment of lesions involving the region of the tuberculum sellae, planum sphenoidale, supradiaphragmatic intradural space, and medial cavernous sinus. The parasellar region of 50 formalin‐fixed cadaveric heads was examined by using magnification 3× to 40×. The arterial and venous systems of five cadaveric specimens were injected under pressure with colored silicone rubber. The sellar region of three specimens was examined histologically. Important anatomic landmarks identified in the roof of the sphenoid sinus include a carotid and trigeminal prominence, as well as a tubercular, clival, and opticocarotid recess. The diaphragma sella is actually comprised of two layers of dura, with a venous system (circular sinus) interposed between the layers. The dura mater of the pituitary gland separates the gland from the medial compartment of the cavernous sinus. The microanatomic detail necessary to extend the transsphenoidal approach to the supradiaphragmatic intradural space and medial compartment of the cavernous sinus is described. These data are presented to facilitate the clinical application of these extended approaches. Clin. Anat. 14:1–9, 2001.

Brain energy metabolism in the acute stage of experimental subarachnoid haemorrhage: Local changes in cerebral glucose utilization

SummaryAn experimental model was used to investigate acute alterations of cerebral metabolic activity in rats subjected to subarachnoid haemorrhage (SAH). Haemorrhages were produced in anaesthetized animals by injecting 0.3 ml of autologous, arterial nonheparinized blood into the cisterna magna. Control rats received subarachnoid injections of mock-cerebrospinal fluid to study the effect of sudden raised intracranial pressure, or underwent sham operation. Three hours after SAH rats were given an intravenous injection of [14C]-2-deoxyglucose. Experiments were terminated by decapitation, and the brains were removed and frozen. Regional brain metabolic activity was studied by quantitative autoradiography. In comparison with sham-operated controls, cerebral metabolic activity was diffusely decreased after SAH. Statistically significant decreases in metabolic rate were observed in 23 of 27 brain regions studied. Subarachnoid injections of mock-cerebrospinal fluid also produced depression of cerebral metabolic activity, but quantitatively these changes were not as pronounced and diffuse as in SAH rats. The present study shows that a widespread depression of brain metabolism occurs in the acute stage after experimental SAH and is probably secondary to the Subarachnoid presence of blood itself and/or blood products.

The Enigmatic Foramen Lacerum

OBJECTIVE The microanatomic details of the foramen lacerum and surrounding region are described to clarify the relationship between the internal carotid artery and the foramen lacerum. The terminology related to these structures is reevaluated. Examples of pathological abnormalities restricted to the foramen lacerum region are presented to document the clinical relevance of this region. METHODS Microanatomic dissections were performed in 12 formalin-fixed cadaveric specimens. Bony landmarks were examined in 50 dry skulls. Microscopic sections of the region were obtained from cadaveric specimens that were formalin-fixed, decalcified, and processed for histological examination. RESULTS The foramen lacerum is not a true foramen. No significant structures traverse its fibrocartilage. In this region, the bony and fibrous structures surround the internal carotid artery to form an incomplete canal, which serves as the rostral extension of petrous canal. CONCLUSION The term foramen lacerum should be restricted to that portion of the cranial base at the confluence of the petrous portion of the temporal, basioccipital, and basisphenoid bones that in vivo is filled with fibrocartilage. The region immediately above the foramen lacerum, occupied by the internal carotid artery and traditionally considered the upper portion of the foramen lacerum, should be considered, anatomically and functionally, to be the rostral extension of the petrous canal. We suggest calling this extension the lacerum portion of the carotid canal.

Cervical subarachnoid hematoma of unknown origin: case report.

Summary Objective and Importance. Spontaneous spinal subarachnoid hematoma is rare, having been reported in the English literature in only seven other cases. We describe the first case of spontaneous subarachnoid hematoma located in the cervical spinal cord of a 43-year-old man. The pathologic examination showed no apparent source of bleeding, but there was evidence of cervical spondylotic myelopathy. Clinical Presentation. The patient presented with a 10-day history of severe neck pain, followed by the onset of quadriparesis that was more evident on the left side, urinary retention, and sensory loss below C5. His medical history included hypertension. Magnetic resonance imaging showed a massive hemorrhage in the cervical spinal canal. Intervention. A C4-C5 subarachnoid hematoma was removed. The patient died due to respiratory distress and uncontrollable hypotension on day 6 after surgery. Surgical exploration, neuroradiologic examinations, and autopsy showed no evidence of vascular malformations, tumors, or other possible sources of bleeding. Conclusion. After excluding more common causes of spontaneous subarachnoid hematoma in this patient, we suggest that chronic spinal cord compression (spondylotic myelopathy) and arterial hypertension in this patient may have caused the pathogenesis of this rare clinical entity. Experimental data supporting this hypothesis are discussed.

Chronic encapsulated intracerebral hematoma: contribution of thallium-201 single photon emission computed tomography in preoperative diagnosis: case report.

OBJECTIVE AND IMPORTANCE Chronic encapsulated intracerebral hematoma is a fairly rare clinical entity. This unique lesion is peculiar for its clinical onset, formation of a capsule, and progressive enlargement. The mechanism for capsule formation and self-perpetuating expansion still remains uncertain, as well as the causal relationship with vascular malformations. Because of their pseudotumoral course and misleading neuroradiological features, these lesions can be misdiagnosed preoperatively as cerebral neoplasms. CLINICAL PRESENTATIONS A 62-year-old man was referred with a 2-month history of generalized tonicoclonic seizures. There was no history of head injury or arterial hypertension. The results of a neurological examination were normal. Computed tomographic scans revealed a slightly hyperdense roundish area in the right parietotemporal region with ring-like enhancement after contrast medium injection, moderate mass effect, and perifocal low attenuation. With the provisional diagnosis of astrocytoma, the patient was admitted for a craniotomy. Before surgery, a thallium-201 single photon emission computed tomographic study was performed, which showed no abnormal uptake of the tracer, raising significant doubt regarding the presumptive diagnosis of a tumor. INTERVENTION Intraoperative findings revealed a hematoma, with a well-demarcated, thick, fibrous-elastic capsule. There was evidence of repeated intracapsular hemorrhages. The lesion was totally removed, and the patient recovered fully. No other pathological findings, including vascular malformations, were noted. CONCLUSION Chronic encapsulated intracerebral hematomas probably occur more frequently than the limited number of reported cases would indicate. This case represents a realistic clinical problem-solving setting in with thallium-201 single photon emission computed tomography was used because of its capacity for functional tumor detection and differential diagnosis.

Pituitary metastasis from uterine cervical carcinoma: a case presenting as diabetes insipidus

The authors report a case of symptomatic pituitary metastasis from an adenocarcinoma of the uterine cervix. Only two cases of intrasellar metastasis from an adenocarcinoma of the uterine cervix have been previously reported; both were identified at autopsy. Our patient presented with clinical features of diabetes insipidus and a right sixth nerve palsy. Trans-sphenoidal surgery was performed and partial removal of the tumour was achieved. The tumour was an epidermoidal carcinoma of the uterine cervix located primarily in the posterior lobe of the pituitary. The patients neurological symptoms were relieved following surgery. The possibility of a secondary location must always be considered in a differential diagnosis when treating an intrasellar lesion in a patient with a documented primary malignancy.The authors report a case of symptomatic pituitary metastasis from an adenocarcinoma of the uterine cervix. Only two cases of intrasellar metastasis from an adenocarcinoma of the uterine cervix have been previously reported; both were identified at autopsy. Our patient presented with clinical features of diabetes insipidus and a right sixth nerve palsy. Trans-sphenoidal surgery was performed and partial removal of the tumour was achieved. The tumour was an epidermoidal carcinoma of the uterine cervix located primarily in the posterior lobe of the pituitary. The patients neurological symptoms were relieved following surgery. The possibility of a secondary location must always be considered in a differential diagnosis when treating an intrasellar lesion in a patient with a documented primary malignancy.