Nolan Altman

The connectivity of the superior longitudinal fasciculus: a tractography DTI study.

PURPOSE The left superior longitudinal fasciculus (SLF) has been felt to link receptive with expressive language areas. The latter is located in the pars opercularis (Brocas area) of the left inferior frontal gyrus. We report the findings with tractography of the SLF in a group of normal volunteers. METHODS AND MATERIALS The data and subsidiary results of 12 normal right-handed volunteers who participated in an institutional review board-approved diffusion tensor imaging study were evaluated. The SLF fibers were obtained bilaterally placing a region of interest at the triangular-shaped region lateral to each of the corticospinal tracts, in a coronal plane along the rostral aspect of the corpus callosum. A sagittal fractional anisotropy image was used to determine the rostral endpoint of the SLF fibers in the white matter pertaining to specific gyri or pars of the frontal lobe. The SLF projection to Brocas area was ranked qualitatively as none, minimal, most or all. Findings are presented in descriptive statistics. RESULTS The SLF projection to Brocas areas was absent in seven subjects (58.3%) and minimal in five (41.6%). SLFs rostral end points were found uniquely or mainly in the precentral gyrus in 100% of cases. CONCLUSION The SLF was found connecting the posterior language areas to the precentral gyrus and only marginally in some cases to the canonical Brocas area. This finding is consistent with reports describing lack of correlation between lateralization of the SLF and language areas. The understanding of language circuitry is beginning to emerge with the use of tractography.

False lateralization of language cortex on functional MRI after a cluster of focal seizures

fMRI can define language cortex but its limitations are not yet fully understood. This article describes a child in whom fMRI falsely lateralized language cortex when performed after a cluster of left temporal lobe seizures. Multiple language tasks revealed no activation over the left temporal lobe despite a normal neurologic exam at the time of the study. A second fMRI performed 2 weeks later activated sites predominantly over the left, which were confirmed by extra-operative functional language mapping. fMRI may be unhelpful after frequent seizures.

The use of stereotactic radiosurgery to treat intractable childhood partial epilepsy.

Summary:  Purpose: Although conventional surgery is presently used to treat seizures of temporolimbic and neocortical origin, deep‐seated lesions are often associated with morbidity. Stereotactic radiosurgery is a noninvasive procedure that effectively treats patients with vascular malformations and brain tumors, but its efficacy for epileptogenic foci is limited, especially in children.

Conventional and Advanced MRI Features of Pediatric Intracranial Tumors: Supratentorial Tumors

OBJECTIVE. Our objective is to review the imaging characteristics and applications of conventional and advanced neuroimaging techniques of supratentorial intracranial masses in the pediatric population. Specifically, we review astrocytomas, oligodendrogliomas, primary neuroectodermal tumors, dysembryoplastic neuroepithelial tumors, gangliogliomas, arachnoid cysts, and choroid plexus and pineal region masses. CONCLUSION. Advanced imaging methods, such as MR spectroscopy, perfusion MRI, functional MRI, diffusion-tensor imaging, and tractography, help develop a more accurate differential diagnosis and aid in planning tumor treatment.

Conventional and Advanced MRI Features of Pediatric Intracranial Tumors: Posterior Fossa and Suprasellar Tumors

OBJECTIVE In this article, we review the most common posterior fossa and suprasellar intracranial neoplasms in the pediatric population. We briefly discuss basic MRI concepts used in the initial evaluation of a pediatric brain tumor and then discuss sophisticated MRI techniques that give insight into the physiology and chemical makeup of these tumors to help the radiologist make a more specific diagnosis. CONCLUSION Diagnosis and treatment of pediatric CNS tumors necessitate a multi-disciplinary approach and require expertise and diligence of all parties involved. Imaging is an essential component has evolved greatly over the past decade. We are becoming better at making a preoperative diagnosis of that tumor type, detecting recurrence, and guiding surgical management to avoid injury to vital brain structures.

Hemangiomas revisited: the useful, the unusual and the new

Hemangiomas are common vascular tumors occurring in children. Though most of the lesions present in infants and young children with a typical appearance, it is important to understand that they all do not behave in the same way. Rather, they are a group of vascular lesions with different clinico-pathological subtypes, with their clinical behavior varying with the stage of the tumor as well. As such, they can and do have a varied clinical, imaging and pathological appearance according to the location of the tumor and also the stage at which the patient is seen. In this pictorial essay, the classification, pathogenesis, clinical appearance, natural history and imaging characteristics of hemangiomas are reviewed and illustrated.

Evidence-based medicine: neuroimaging of seizures

Evidence-based medicine is useful in epilepsy and neuroimaging (Figs. 1 and 2). An understanding of the pretest probability suggests that focal neurologic deficits are important in predicting the outcome of neuroimaging examinations. In cases of nonacute symptomatic seizures, confusion and postictal deficits should prompt MR evaluation. In remote symptomatic seizures, MR imaging should be performed in a child with unexplained cognitive or motor delays or a child less than 1 year of age. Patients with partial seizures, abnormal EEG, or generalized epilepsy also should be imaged. Acute seizures should be imaged with CT to exclude hemorrhage and because of the availability and speed of the modality. Ictal SPECT is the best neuroimaging examination to localize seizure activity. MR imaging can offer prediction of surgical outcome and may hold promise in the future for dimensional localization of seizure focus. Evidence-based medicine can only work if there is physician communication. The pretest probability is helpful only when an accurate history is provided to the consulting physician. This field will flourish if physicians can develop accurate methods of collating information and reporting it in a timely fashion in the literature.

Neural Networks of Motor and Cognitive Inhibition are Dissociated Between Brain Hemispheres: An fMRI Study

Paradigms exploring cognitive inhibition involve motor responses, which may confound the results. We compare cognitive inhibition activation obtained without motor involvement, to motor inhibition alone, in a group of young right-handed volunteers, utilizing a classical color Stroop task (CST), and a Stop Task. Comparison of fMRI activation was performed contrasting lateralization indexes of different Regions of Interest (ROI). Cognitive inhibition showed left brain lateralization, while motor inhibition showed right brain lateralization. Homologue brain areas involved the inferior frontal gyrus, inferior parietal lobule, middle temporal gyrus, and anterior cingulate gyrus. These circuitries appear to support that inhibition is a complicated function involving working memory, attention, semantic decision, and motivation modules.

Imaging the brachial plexus and peripheral nerves in infants and children.

Imaging of the brachial plexus and peripheral nerves is challenging in the pediatric patient. Magnetic resonance imaging is the modality of choice as it is not invasive and demonstrates proximal and distal lesions. This may be used to detect nerve root avulsions, nerve ruptures, pseudo-meningoceles, brachial plexus scarring, post-traumatic neuromas, brachial plexus edema, spinal cord damage, abnormalities of the shoulder joint, trauma, neoplasms, and infection. Imaging allows diagnosis and careful preoperative evaluation of children suffering from brachial plexus injuries and peripheral nerve disorders.

CT and MRI of pleomorphic xanthoastrocytoma: unusual biologic behavior.

Objective Our goal was to present three cases of pleomorphic xanthoastrocytoma (PXA) with unusual radiographic, clinical, and pathologic aspects. Materials and Methods The imaging findings in three patients with proven PXA were reviewed and correlated with clinical information and review of pathologic material. Two females and one male were studied, ranging in age from 8 to 42 years old. All patients underwent MRI with gadolinium (0.1 mmol/kg). Two of the patients had serial MR studies. CT scans with and without contrast agent were also available for two patients. The medical records for all three patients were reviewed. Radiographic findings were correlated with pathologic material obtained at surgery. Results Seizure disorder was the initial presentation in two patients. The third patient presented with a lytic lesion of the calvarium. Radiographic features showed rapid progression of disease over 3 months in one patient. Rapid tumor recurrence (within 7 months) without malignant transformation was proven in another patient. While typical pathological features of PXA were evident in two cases, a mixed tumor consisting of PXA and other tissue components was identified in the third case. Conclusion Although generally regarded as a benign lesion in the literature, PXA has potential for aggressive behavior. Rapid tumor recurrence can occur without tnalignant transformation. Radiographic features may evolve over a short period of time. Dura and bony calvarium are not necessarily respected. PXA can occur as a separate entity or as a tumor of mixed components.