MRI atlas of the human hypothalamus.

Gaining new insights into the anatomy of the human hypothalamus is crucial for the development of new treatment strategies involving functional stereotactic neurosurgery. Here, using anatomical comparisons between histology and magnetic resonance images of the human hypothalamus in the coronal plane, we show that discrete gray and white hypothalamic structures are consistently identifiable by MRI. Macroscopic and microscopic images were used to precisely annotate the MRI sequences realized in the coronal plane in twenty healthy volunteers. MRI was performed on a 1.5 T scanner, using a protocol including T1-weighted 3D fast field echo, T1-weighted inversion-recovery, turbo spin echo and T2-weighted 2D fast field echo imaging. For each gray matter structure as well as for white matter bundles, the different MRI sequences were analyzed in comparison to each other. The anterior commissure and the fornix were often identifiable, while the mammillothalamic tract was more difficult to spot. Qualitative analyses showed that MRI could also highlight finer structures such as the paraventricular nucleus, the ventromedial nucleus of the hypothalamus and the infundibular (arcuate) nucleus, brain nuclei that play key roles in the regulation of food intake and energy homeostasis. The posterior hypothalamic area, a target for deep brain stimulation in the treatment of cluster headaches, was readily identified, as was the lateral hypothalamic area, which similar to the aforementioned hypothalamic nuclei, could be a putative target for deep brain stimulation in the treatment of obesity. Finally, each of the identified structures was mapped to Montreal Neurological Institute (MNI) space.

Masseter muscle termination over the deep surface of the temporal fascia: look out the wrong path.

PURPOSE: The masticatory muscles have a common embryological origin. Despite numerous anatomical studies their close anatomical relationships are not always accurately described in anatomical treatises. An expansion of the masseter muscle inserted into the deep surface of the superficial temporal aponeurosis has been described. Despite the classical description of two transition bundles (Yoshikawa et al. in Kaibogaku Zasshi 37:206-217, 1962), the literature concerning these fibres has remained difficult to interpret. Given the clinical applications of the lengthening of the temporal muscle in myoplasty, it is important that we have accurate anatomical knowledge of it. METHODS: We dissected 14 embalmed or untreated anatomical cadaver heads with a sex ratio of 1 in order to analyse the aforementioned fibres and their variations. A radiologic study allowed us to understand the entanglement of the fibres. 10 craniofacial MRI were processed by 3D MPR reconstruction. RESULTS: The fibres were identified as an expansion of the posterior head of the masseter muscle and distinct from the two classically described transition bundles. These were present in all subjects of both sexes. We can systematically describe their origin, trajectory and termination. CONCLUSION: Fibres belonging to masseter muscle pass up to the zygomatic arch and terminate on the deep surface of the temporal fascia. Awareness of the nature and trajectory of these muscular fibres allows us to avoid taking "wrong path" when approaching the temporal muscle tendon on the coronoid process via the temporal fossa.

Sex steroid hormones-related structural plasticity in the human hypothalamus.

We investigated the effects of an artificial menstrual cycle on brain structure and activity in young women using metabolic magnetic resonance imaging (MRI). We show that the activation of the hypothalamo-pituitary-gonadal axis during the pill-free interval of low-dose combined oral contraceptive use is associated with transient microstructural and metabolic changes in the female hypothalamus but not in the thalamus, a brain structure unrelated to reproductive control, as assessed by water diffusion and proton magnetic resonance spectra measurements. Our results provide neuroanatomical insights into the mechanism by which sex steroid hormones mediate their central effects and raise the intriguing possibility that specific regions of the neuroendocrine brain use ovarian cycle-dependent plasticity to control reproduction in humans. These MRI-based physiological studies may pave the way for the development of new diagnostic and treatment strategies in the central loss of reproductive competence in human syndromes, such as hypothalamic amenorrhea.

Adrenal gland hypertrophy in a case of homolateral renal agenesis: case report with special emphasis on adrenal blood supply.

Hypertrophic suprarenal gland is an anomaly which can lead to serious complications during adrenalectomy under endoscopy because of abnormal veins of the retroperitoneum. The authors report a rare dissection of a male which presented with this anomaly in a case of homolateral renal agenesis, highlighting this left pseudorenal vein. No abnormality of the genital tract was found. The anatomic features, associated syndromes, implications for endoscopic surgery are outlined and embryologic considerations and discussed.

Surgical resection of thalamic tumors in children: approaches and clinical results.

OBJECTIVES: Thalamic tumors are uncommon, and although gross total removal (GTR) is a prospective goal, its interest is debated because the thalamus constitutes a highly functional region. The relation of choice of the surgical approach, achievability of GTR, and operative morbidity to the anatomic location of the tumor has received little attention in the medical literature. MATERIALS AND METHODS: We reviewed retrospectively the cases of pediatric patients treated for thalamic tumor, with pre- and postoperative magnetic resonance imaging, and who were operated with the aim of maximal surgical removal. CONCLUSION: We reviewed 16 cases operated between 1992 and 2003. The clinical presentation was dominated by intracranial hypertension and hemiparesis. Fifteen children were operated through transcortical approaches: transfrontal in six cases, transparietal in six, and transtemporal in three. The remaining patient was operated through an infratemporal approach. All operations performed since 1998 used intraoperative neuronavigation. Complete or near-total resection was achieved in 11 cases; only subtotal resection was achieved in the remaining five cases. The most common postoperative morbidity was visual field defect. Hemiparesis was unchanged or improved in all the cases. Seven children died of tumor progression, in relation with high histological grade, and one died of acute hydrocephalus. The approach to thalamic tumors needs to be planned according to the location of critical neural structures. GTR of thalamic tumors in children bears acceptable morbidity and may even improve preoperative deficits. Surgery alone can be curative in low-grade tumors; in high-grade or infiltrating tumors, GTR is only part of the overall oncological management.

MRI location of the distal dural ring plane: anatomoradiological study and application to paraclinoid carotid artery aneurysms.

The distal dural ring plane (DDRP) separates the intradural from the extradural paraclinoid internal carotid artery. The purpose of this study was to evaluate its position with MR imaging. The protocol used a T2-weighted sequence in two orthogonal planes: diaphragmatic (DIA-P) and carotid (CAR-P). The DDRP passes through four anatomoradiological reference points (RefP). We developed on a cadaveric model a correlation method supported by correlation lines and angles (CA) projecting the RefP toward the DDRP. RefP were correlated to the DDRP in 65-84% of cases in the DIA-P and 60-76% of cases in the CAR-P. CA were identified and correlated to the DDRP, respectively, in 87% and 60% of cases in the DIA-P, and 60% and 51% of cases in the CAR-P (failure often related to a lack of visibility of just one RefP). A higher tissular contrast in living subjects allowed the identification of CA in 90% and 80% of cases, respectively, in the DIA-P and the CAR-P. We propose that CA, when identified, should be considered as an approximation of the inferior radiological limit of the DDRP curve. In difficult angiographical cases, this MRI protocol could help to locate paraclinoid aneurysms on both sides of the cavernous sinus roof.

Sonographic mapping of the normal brachial plexus.

BACKGROUND AND PURPOSE: Mapping of the brachial plexus with MR imaging has been reported and may have potential clinical applications (eg, precise localization of traumatic or tumoral nerve lesions, selective anesthesia of the brachial plexus). We sought to demonstrate that mapping of the brachial plexus may be performed by means of sonography. METHODS: Twelve healthy adult volunteers (seven women and five men; age range, 24-38 years; mean, 31 years) underwent bilateral sonographic examination for the assessment of the nerve structures of the brachial plexus from the extraforaminal part to the axillary part. Four formolated cadavers (two male and two female; age range, 66-84 years; mean, 77.5 years) were frozen and sawed into 3-mm-thick contiguous sections in the same plane as that used for the sonographic exploration. RESULTS: A satisfactory sonographic examination was performed in 10 of 12 volunteers, leading to a good association with anatomic sections. Two volunteers were excluded from the study because a clear depiction of the brachial plexus was difficult owing to a short neck and low echogenicity at examination. The association between sonographic images and anatomic sections allowed us to map the brachial plexus. The subclavian and deep cervical arteries were useful landmarks for this mapping. The eighth cervical nerve root and the first thoracic nerve root were the most difficult part of the brachial plexus to depict because of their deep location. CONCLUSION: The brachial plexus can be mapped with sonography. However, this technique requires a good grounding in anatomy and may be impossible in short-necked individuals.