Faculty Bibliography

In Drosophila, the transcription factor glial cells missing (gcm) is believed to play a central role in the cell-fate specification of glia. Two mammalian homologs of gcm have been identified (Gcm1 and Gcm2) but little is known about their roles in the CNS. Expression studies indicate that these genes are highly expressed in non-neural tissues. However, we previously reported a low level of Gcm1 in the developing mouse CNS. To assess the potential function of Gcm1 in CNS development, we generated transgenic mice that express Gcm1 under the control of the Hoxa7 enhancer. Five independent transgenic lines were obtained, all of which transiently express Gcm1 (E9 to E13.5) from the mid-thoracic level to the tailbud. We reported that ectopic expression of Gcm1 during early embryogenesis induces severe neural tube defects that have counterparts in human diseases: failure of the neural tube to close (spina bifida) and multiple ectopic neural tubes (diastematomyelia). In the tailbud, mesenchymal cells expressing Gcm1 form secondary neural tubes, which express beta3-tubulin and the motoneuron marker islet-1. The analysis of glial cell types in these ectopic neural tubes revealed also the presence of oligodendrocyte precursors and differentiated astrocytes. We showed that ectopic expression of Gcm1 in multipotential mesenchymal cells of the tailbud overrides a mesodermal cell fate and instead drives them towards a neural pathway. Thus, Gcm may play a conserved role in neural specification throughout evolution

A rare complication of transbronchoscopic lung biopsy, namely a cerebral air embolism, is presented. The course of events following the embolic episode in the form of a fall in blood pressure, bradycardia and convulsions is documented, as is the presence of an air emboli on the CT scan of the brain with subsequent resorption of the emboli on the follow-up scan. The salient features of the case are the rarity of the complication and the excellent temporal depiction of imaging findings on CT scan demonstrated as resorption of air emboli and subsequent watershed territory infarcts

Magnetic resonance spectroscopy (MRS) has been shown to be an effective noninvasive diagnostic tool that can be used to monitor serially biochemical and metabolic changes in serial disease processes that affect the brain. MRS is now a clinical tool that is reimbursable. This article reviews MRS physics, techniques, pulse sequences, and the clinical applications of MRS

BACKGROUND AND PURPOSE: The choline (Cho)/creatine (Cr) ratio has been shown to be a reliable proton MR spectroscopy metabolic marker for differentiating squamous cell carcinoma (SCCA) from normal muscle in the upper aerodigestive tract. However, it is unclear whether the Cho/Cr ratio can be used to differentiate a malignant tumor from a benign neoplasm in the extracranial head and neck. Our purpose was to determine whether the Cho/Cr ratio can be used to differentiate benign from malignant tumors in this region. METHODS: In vitro one-dimensional proton MR spectroscopy (2,000/136,272 [TR/TE]) was performed at 11 T on tissue specimens obtained from glomus tumors (n = 3), inverting papilloma (n = 1), and schwannoma (n = 1). Cho/Cr area ratios were calculated and compared with similar, previously reported in vitro (11 T) findings and with samples of SCCA and normal muscle. RESULTS: The Cho/Cr ratio was elevated in relation to muscle in all benign tumors at TE = 136 (glomus tumors = 4.52, inverting papilloma = 3.85, schwannoma = 2.2) and at TE = 272 (glomus tumors = 8.01, inverting papilloma = 2.1, schwannoma = 4.28). The average Cho/Cr ratio for benign lesions was 3.92 (TE = 136) and 6.11 (TE = 272). The Cho/Cr ratio was significantly higher in benign tumors than in both SCCA and muscle. The average Cho/Cr ratio for muscle at TEs of 136 and 272 was 1.16 and 1.31, respectively, whereas for SCCA the average Cho/Cr ratio at TEs of 136 and 272 was 1.67 and 2.45, respectively. CONCLUSION: In our small group, the Cho/Cr ratio was significantly higher in benign tumors than in muscle and SCCA of the extracranial head and neck

PURPOSE: To evaluate the length and width of the bony canal of the cochlear nerve in patients with congenital sensorineural hearing loss (SNHL) who have 'normal' findings at thin-section computed tomography (CT) of the temporal bone. MATERIALS AND METHODS: The authors retrospectively evaluated the length and width of the bony canal for the cochlear nerve in two groups of patients. The first group was composed of 33 patients with profound SNHL and no demonstrable abnormality at thin-section CT. The control group was composed of 50 patients who underwent temporal bone CT for causes unrelated to SNHL. The mean value +/- SD was calculated for both cohorts. Statistical analysis consisted of the nonparametric Wilcoxon rank sum test with the NPAR1WAY program. RESULTS: The length and width of the bony canal for the cochlear nerve were significantly smaller in patients with SNHL than in the control group (P <.05) CONCLUSION: The hypoplastic bony canal for the cochlear nerve in patients with SNHL may be indicative of a previously unrecognized embryologic malformation of the cochlear nerve

Fetus in fetu is a rare abnormality secondary to the abnormal embryogenesis in a diamniotic, monochorionic pregnancy. It is an unusual condition in which a vertebrate fetus is enclosed within the abdomen of a normally developing fetus. Presented are the computed tomographic findings in two cases in which imaging findings were diagnostic of this entity

BACKGROUND AND PURPOSE: The sphenoid sinus is rarely implicated as a site of spontaneous CSF fistula. We undertook this study to evaluate the potential etiopathogenesis of spontaneous CSF fistula involving the sphenoid sinus and to review the imaging findings. METHODS: We retrospectively reviewed the imaging findings of 145 cases of CSF fistula from our departmental archives (August 1995 through August 1998). Fifteen (10%) patients had CSF fistulas involving the sphenoid sinus. Eleven (7%) patients had spontaneous CSF fistulas, whereas in four patients, the CSF fistulas in the sphenoid sinus were related to trauma. Of the 11 patients, nine underwent only plain high-resolution CT and MR cisternography. One patient additionally underwent contrast-enhanced CT cisternography, and one other patient underwent MR cisternography only. For each patient, the CSF fistula site was surgically confirmed. The MR imaging technique included T1-weighted and fast spin-echo T2-weighted 3-mm-thick coronal sequences obtained with the patient in the supine position. The plain high-resolution CT study included 3-mm-thick, and sometimes 1- to 1.5-mm-thick, coronal sections obtained with the patient in the prone position. Similar sections were obtained after injecting nonionic contrast material intrathecally via lumbar puncture for the CT cisternographic study. We evaluated each of the 11 patients for the exact site of CSF leak in the sphenoid sinus. We also determined the presence of pneumatization of lateral recess of the sphenoid sinus, orientation of the lateral wall of the sphenoid sinus, presence of arachnoid pits, presence of brain tissue herniation, and presence of empty sella in each of these patients. RESULTS: The exact sites of the CSF fistulas were documented for all 11 patients by using plain high-resolution CT, MR cisternography, or CT cisternography. In nine (82%) patients, the sites of the CSF fistulas were at the junction of the anterior portion of the lateral wall of the sphenoid sinus and the floor of the middle cranial fossa. In the remaining two (18%) patients, the sites of the CSF fistulas were along the midportion of the lateral wall of the sphenoid sinus. Of these 11 patients, one had bilateral sites of the CSF fistula at the junction of the anterior portion of the lateral wall of the sphenoid sinus with the floor of the middle cranial fossa. In nine (82%) patients, the presence of brain tissue herniation was revealed, and this finding was best shown by MR cisternography. Ten (91%) patients had extensive pneumatization of the lateral recess of the sphenoid sinus, with an equal number having outward concave orientation of the inferior portion of the lateral wall of the sphenoid sinus. In seven (63%) patients, the presence of arachnoid pits, predominantly along the anteromedial aspect of the middle cranial fossa, was shown. In seven (63%) patients, empty sella was shown. For comparison, we reviewed the CT studies of the paranasal sinuses in 100 age-matched control subjects from a normal population. Twenty-three had extensive lateral pneumatization of the sphenoid sinus along with outward concavity of the inferior portion of the lateral wall. None of these 23 patients had arachnoid pits. CONCLUSION: The sphenoid sinus, when implicated as a site of spontaneous CSF leak, yields a multitude of imaging findings. These are extensive pneumatization of the lateral recess of the sphenoid sinus, outward concave orientation of the inferior portion of the lateral wall of the sphenoid sinus, arachnoid pits, and empty sella. Considering the normative data, we speculate that this constellation of findings could play a role in the etiopathogenesis of spontaneous sphenoid sinus fistulas. Our findings also show the efficacy of noninvasive imaging techniques, such as plain high-resolution CT and MR cisternography, in the evaluation of sphenoid sinus CSF leak. Our data also suggest that spontaneous sphenoid sinus CSF leak is not an uncommon occurrenc

One of the most challenging topics for radiologists is congenital anomalies arising from abnormal embryogenesis of the branchial apparatus. Defects of the branchial apparatus result in a spectrum of anomalies that includes fistulas, sinuses, cysts, temporal bone anomalies, craniofacial malformations, and systemic disorders. A better understanding of the various radiologic abnormalities is aided by an understanding of their embryonic origins. This article reviews the spectrum of abnormalities that are secondary to anomalous embryogenesis of the branchial arches

Fungal diseases of the paranasal sinuses can be categorized into the invasive and noninvasive varieties. The invasive form has been classified as acute fulminant fungal sinusitis, granulomatous invasive fungal sinusitis, and chronic invasive fungal sinusitis. The noninvasive form can be classified as the fungus ball and the allergic fungal sinusitis. The following review discusses the various types of fungal sinusitis with a special emphasis on the CT and MR imaging features

PURPOSE: Knowledge of the normal anatomy of the four bony canals located at the fundus of the internal auditory canal (IAC) is necessary during evaluation of temporal bone trauma, congenital anomalies affecting the individual nerves, and some neuro-otologic surgeries. The purpose of this work was therefore to characterize the normal appearance of the four bony canals and to measure their dimensions. METHOD: A retrospective study was performed using CT studies of the temporal bones in 50 patients to identify and characterize the bony canals for the labyrinthine segment of the facial nerve (BCFN), superior vestibular nerve (BCSVN), cochlear nerve (BCNC), and the inferior vestibular nerve (singular canal; SC) located at the fundus of the IAC. All the patients underwent high resolution temporal bone CT for evaluation of uncomplicated inflammatory (n = 49) and neoplastic (n = 1) diseases involving the temporal bone. CT studies were done using 1-mm-thick contiguous sections in axial and coronal planes. Measurements of the canals were performed by one radiologist. No patient had a prior history of trauma, vertigo, and sensorineural hearing loss or facial nerve paralysis. RESULTS: The BCFN, BCSVN, and BCNC were identified in all studies, whereas the SC was seen in 93% of studies. The BCFN, BCSVN, and BCNC arise from the fundus of the IAC, whereas the SC arises medial to the fundus. Mean +/- SD measurements (in mm) of the length and width were as follows: BCFN = 2.92+/-0.48 and 0.91+/-0.28; BCSVN = 2.36+/-0.53 and 0.89+/-0.28; BCNC = 0.93+/-0.21 and 2.13+/-0.44; and SC = 3.22+/-0.73 and 0.50+/-0.14. CONCLUSION: These small canals are routinely visualized on thin section (1 mm) CT of the temporal bone and should not be confused with fractures. This study provides baseline measurements that may be used to evaluate congenital anomalies of these canals. These data may also be helpful in the presurgical evaluation of patients undergoing singular neurectomies for benign positional vertigo