Minimally Invasive Approaches for Anterior Skull Base Meningiomas: Supraorbital Eyebrow, Endoscopic Endonasal, or a Combination of Both? Anatomic Study, Limitations, and Surgical Application

BACKGROUND

Minimally invasive accesses to the anterior skull base include the endoscopic endonasal approach (EEA) and the supraorbital eyebrow approach. These 2 are often seen as competing approaches, not alternative or combinatory approaches. In this study, we evaluated the anatomic limitations of each approach and the combined approach for accessing the anterior skull base.

METHODS

Ten neurovascular injected cadaver heads were used for the study. The supraorbital approach to the anterior skull base was performed on 5 heads, and EEA was done on the other 5 heads. Then, the supraorbital approach was added to the 5 heads receiving EEA. Visualization and surgical limitations were recorded by the ability to perform resection of the crista galli, anterior clinoid, cribriform plate, and planum sellae.

RESULTS

The maximal lateral extension of EEA for anterior skull base was the midorbit line anteriorly but narrowing down toward the orbital apex. The limitation of the supraorbital approach was found mostly medial and anterior. Drilling of anterior skull base was impossible medially between the sphenoethmoidal suture and the posterior aspect of the crista galli. The combined approach showed complementary areas of visualization and surgical maneuverability. Three clinical cases were presented to illustrate the indications for the stand-alone supraorbital approach, EEA, and combined approach.

CONCLUSION

The limitations of the EEA when dealing with lateral extension of anterior skull base meningiomas, and the limitations of the supraorbital eyebrow approach for medial skull base drilling and reconstruction, can be overcome by a judicious, anatomically based combination of both approaches.

A diffusion spectrum imaging-based tractographic study into the anatomical subdivision and cortical connectivity of the ventral external capsule: uncinate and inferior fronto-occipital fascicles

PURPOSE

The inferior fronto-occipital fasciculus (IFOF) and uncinate fasciculus (UF) are major fronto-capsular white matter pathways. IFOF connects frontal areas of the brain to parieto-occipital areas. UF connects ventral frontal areas to anterior temporal areas. Both fascicles are thought to subserve higher language and emotion roles. Controversy pertaining to their connectivity and subdivision persists in the literature, however.

METHODS

High-definition fiber tractography (HDFT) is a non-tensor tractographic method using diffusion spectrum imaging data. Its major advantage over tensor-based tractography is its ability to trace crossing fiber pathways. We used HDFT to investigate subdivisions and cortical connectivity of IFOF and UF in 30 single subjects and in an atlas comprising averaged data from 842 individuals. A per-subject aligned, atlas-based approach was employed to seed fiber tracts and to study cortical terminations.

RESULTS

For IFOF, we observed a tripartite arrangement corresponding to ventrolateral, ventromedial, and dorsomedial frontal origins. IFOF volume was not significantly lateralized to either hemisphere. UF fibers arose from ventromedial and ventrolateral frontal areas on the left and from ventromedial frontal areas on the right. UF volume was significantly lateralized to the left hemisphere. The data from the averaged atlas was largely in concordance with subject-specific findings. IFOF connected to parietal, occipital, but not temporal, areas. UF connected predominantly to temporal poles.

CONCLUSION

Both IFOF and UF possess subdivided arrangements according to their frontal origin. Our connectivity results indicate the multifunctional involvement of IFOF and UF in language tasks. We discuss our findings in context of the tractographic literature.

Asymmetry, connectivity, and segmentation of the arcuate fascicle in the human brain

The structure and function of the arcuate fascicle is still controversial. The goal of this study was to investigate the asymmetry, connectivity, and segmentation patterns of the arcuate fascicle. We employed diffusion spectrum imaging reconstructed by generalized q-sampling and we applied both a subject-specific approach (10 subjects) and a template approach (q-space diffeomorphic reconstruction of 30 subjects). We complemented our imaging investigation with fiber microdissection of five post-mortem human brains. Our results confirmed the highly leftward asymmetry of the arcuate fascicle. In the template, the left arcuate had a volume twice as large as the right one, and the left superior temporal gyrus provided five times more volume of fibers than its counterpart. We identified four cortical frontal areas of termination: pars opercularis, pars triangularis, ventral precentral gyrus, and caudal middle frontal gyrus. We found clear asymmetry of the frontal terminations at pars opercularis and ventral precentral gyrus. The analysis of patterns of connectivity revealed the existence of a strong structural segmentation in the left arcuate, but not in the right one. The left arcuate fascicle is formed by an inner or ventral pathway, which interconnects pars opercularis with superior and rostral middle temporal gyri; and an outer or dorsal pathway, which interconnects ventral precentral and caudal middle frontal gyri with caudal middle and inferior temporal gyri. The fiber microdissection results provided further support to our tractography studies. We propose the existence of primary and supplementary language pathways within the dominant arcuate fascicle with potentially distinct functional and lesional features.

Chondrosarcomas of the head and neck

Chondrosarcoma represents approximately 11% of all primary malignant bone tumors. It is the second most common sarcoma arising in bone after osteosarcoma. Chondrosarcomas of the head and neck are rare and may involve the sinonasal tract, jaws, larynx or skull base. Depending on the anatomical location, the tumor can produce a variety of symptoms. Computed tomography and magnetic resonance imaging are the preferred imaging modalities. The histology of conventional chondrosarcoma is relatively straightforward; major challenges are the distinction between grade I chondrosarcomas and chondromas, and the differential diagnosis with chondroblastic osteosarcoma and chondroid chordoma. Surgery alone or followed by adjuvant radiotherapy is the treatment of choice. Radiotherapy alone has also been reported to be effective and can be considered if mutilating radical surgery is the only curative alternative. The 5-year survival for chondrosarcoma reaches 80%; distant metastases and/or local recurrences significantly worsen prognosis. The present review aims to summarize the current state of information about the biology, diagnosis and management of these rare tumors.

Rethinking the role of the middle longitudinal fascicle in language and auditory pathways

The middle longitudinal fascicle (MdLF) was originally described in the monkey brain as a pathway that interconnects the superior temporal and angular gyri. Only recently have diffusion tensor imaging studies provided some evidence of its existence in humans, with a connectivity pattern similar to that in monkeys and a potential role in the language system. In this study, we combine high-angular-resolution fiber tractography and fiber microdissection techniques to determine the trajectory, cortical connectivity, and a quantitative analysis of the MdLF. Here, we analyze diffusion spectrum imaging (DSI) studies in 6 subjects (subject-specific approach) and in a template of 90 DSI studies (NTU-90 Atlas). Our tractography and microdissection results show that the human MdLF differs significantly from the monkey. Indeed, the human MdLF interconnects the superior temporal gyrus with the superior parietal lobule and parietooccipital region, and has only minor connections with the angular gyrus. On the basis of the roles of these interconnected cortical regions, we hypothesize that, rather than a language-related tract, the MdLF may contribute to the dorsal "where" pathway of the auditory system.

Microvascular anatomy of the medial temporal region: part 1: its application to arteriovenous malformation surgery

BACKGROUND

The medial temporal region (also called the temporomesial or mediobasal temporal region) is the site of the most complex cortical anatomy.

OBJECTIVE

To investigate the anatomic variability of the arterial supply and venous drainage of each segment of the medial temporal region (MTR), and to discuss and illustrate the implications of the findings for surgery of arteriovenous malformations (AVM) of the MTR.

METHODS

Forty-seven cerebral hemispheres and 10 silicon-injected cadaveric heads were examined using x3 to x40 magnification. Illustrative surgical cases of MTR AVMs were selected.

RESULTS

The anterior choroidal artery (AChA) gave rise to an anterior uncal artery in 83% of hemispheres and a posterior uncal or unco-hippocampal artery in 98%. The plexal segment of the AChA gave off neural branches in 38%. The MCA was the site of origin of anterior uncal, unco-parahippocampal, or anterior parahippocampal arteries in 94% of hemispheres. An anterior uncal artery arose from the internal carotid artery (ICA) in 45% of hemispheres. The posterior cerebral artery (PCA) irrigated the entorhinal area through its anterior parahippocampal or hippocampo-parahippocampal branches in every case. A PCA bifurcation was identified in 89% of hemispheres, typically at the middle segment of the MTR. The most common pattern of bifurcation was by division into posteroinferior temporal and parieto-occipital arterial trunks. The anterior segment of the basal vein had a predominant anterior drainage in 35% of hemispheres, and the middle segment had a predominant inferior drainage in 16%.

CONCLUSION

An understanding of the vascular variability of the MTR is essential for accurate microsurgical resection of MTR AVMs.

Three-dimensional microsurgical and tractographic anatomy of the white matter of the human brain

OBJECTIVE

We sought to investigate the three-dimensional structure of the white matter of the brain by means of the fiber-dissection technique and diffusion-tensor magnetic resonance imaging to assess the usefulness of the combination of both techniques, compare their results, and review the potential functional role of fiber tracts.

METHODS

Fifteen formalin-fixed human hemispheres were dissected according to Klingler's fiber-dissection technique with the aid of 36 to 340 magnification. Three-dimensional anatomic images were created with the use of specific software. Two hundred patients with neurological symptoms and five healthy volunteers were studied with diffusion-tensor magnetic resonance imaging (3 T) and tractographic reconstruction.

RESULTS

The most important association, projection, and commissural fasciculi were identified anatomically and radiologically. Analysis of their localization, configuration, and trajectory was enhanced by the combination of both techniques. Three-dimensional anatomic reconstructions provided a better perception of the spatial relationships among the white matter tracts. Tractographic reconstructions allowed for inspection of the relationships between the tracts as well as between the tracts and the intracerebral lesions. The combination of topographical anatomic studies of human fiber tracts and neuroanatomic research in experimental animals, with data from the clinicoradiological analysis of human white matter lesions and intraoperative subcortical stimulation, aided in establishing the potential functional role of the tracts.

CONCLUSION

The fiber-dissection and diffusion-tensor magnetic resonance imaging techniques are reciprocally enriched not only in their application to the study of the complex intrinsic architecture of the brain, but also in their practical use for diagnosis and surgical planning.

The claustrum and its projection system in the human brain: a microsurgical and tractographic anatomical study

Object

The goal in this study was to examine the microsurgical and tractographic anatomy of the claustrum and its projection fibers, and to analyze the functional and surgical implications of the findings.

Methods

Fifteen formalin-fixed human brain hemispheres were dissected using the Klingler fiber dissection technique, with the aid of an operating microscope at × 6–40 magnification. Magnetic resonance imaging studies of 5 normal brains were analyzed using diffusion tensor (DT) imaging–based tractography software.

Results

Both the claustrum and external capsule have 2 parts: dorsal and ventral. The dorsal part of the external capsule is mainly composed of the claustrocortical fibers that converge into the gray matter of the dorsal claustrum. Results of the tractography studies coincided with the fiber dissection findings and showed that the claustrocortical fibers connect the claustrum with the superior frontal, precentral, postcentral, and posterior parietal cortices, and are topographically organized. The ventral part of the external capsule is formed by the uncinate and inferior occipitofrontal fascicles, which traverse the ventral part of the claustrum, connecting the orbitofrontal and prefrontal cortex with the amygdaloid, temporal, and occipital cortices. The relationship between the insular surface and the underlying fiber tracts, and between the medial lower surface of the claustrum and the lateral lenticulostriate arteries is described.

Conclusions

The combination of the fiber dissection technique and DT imaging–based tractography supports the presence of the claustrocortical system as an integrative network in humans and offers the potential to aid in understanding the diffusion of gliomas in the insula and other areas of the brain.

[Causes of reoperations in patients with lumbar spinal stenosis treated with instrumentations]

OBJECTIVE

In present study we analyze the causes leading to reoperation patients treated for lumbar spinal stenosis with laminectomy and lumbar instrumentation.

MATERIAL AND METHODS

74 patients operated between January of 1996 and December of 2000 with a minimum 4 year follow-up were seleted for the study.

RESULTS

16 patients (21.1%) underwent a new surgical intervention. The main cause for reoperation was stenosis of the adjacent level superiorly to the instrumentation (in 50%). Other causes were radicular fibrosis, persistence of stenosis after the surgery, neuropatic pain, failure of the instrumentation system, transpedicular screws misplacement and break of screws.

CONCLUSIONS

Complications related with the initial surgical procedure are low, as half of the reoperations were due to stenosis of the segment superior to the fixation.

[Brain aneurysms: an infrequent cause of transient ischemic stroke]

INTRODUCTION

Ischemic symptomatology related to the presence of saccular brain aneurysms is infrequent, and this makes it difficult to reach a widespread agreement about the most suitable treatment.

CASE REPORT

A 17-year-old male with symptoms of little stroke produced by distal embolisation of an aneurysm in the middle cerebral artery. The patient was treated by endovascular aneurysm exclusion.

CONCLUSIONS

In patients with no other identifiable cause of ischemic attacks, the possible presence of a brain aneurysm must be taken into account. First choice treatment is the obliteration of the aneurysm using endovascular techniques. If the approach to the aneurysm (either endovascular or surgical) entails a high risk for the patient, another possibility is to use antiplatelet drugs.

[Update in neurocysticercosis treatment]

INTRODUCTION

Neurocysticercosis is the most frequent central nervous system parasitosis, although quite infrequent in our country. Its rising incidence can be explained by immigration from regions of the world where this disease is endemic.

OBJECTIVE

This paper reviews treatment options for this condition. PATIENTS AND METHODS. Eight patients have been diagnosed with neurocysticercosis in the last three years in our hospital. Patient age, sex, origin, symptoms, CT and MR images, diagnostic tests, treatment and duration of medical treatment and clinical and neuroradiological evolution are examined.

RESULTS

Patient age ranged from 25 to 33 years, all eight came from South America and the most frequent initial symptom was an epileptic crisis. Two patients had a single lesion, six had multiple lesions and all eight showed the lesion in the parenchyma. Only 50% showed a positive serum ELISA test for Taenia solium. Initial treatment was surgical in only one patient and the other seven received albendazol. In one of the latter the drug was ineffective and surgery was undertaken. A ten month follow up period has found a favorable evolution in all the patients, who are all also asymptomatic at the present time.

DISCUSSION AND CONCLUSIONS

Neurocysticercosis is more common among immigrants than the local population in Spain. The initial treatment should be medical, with surgery as an option for non responders. We believe that duration of the medical treatment will depend on the patient and the clinico radiological evolution of his/her disease.