Persistent stapedial artery: a congenital anomaly to know.

Persistent stapedial artery, one of the rare arterial congenital anomalies of the middle ear, is important to know due to its possible clinical repercussions. Ignoring its existence may lead to complications during surgery of the middle ear (notably hemorrhage). Exploration of the vascular malformation is rendered possible via high-definition computed tomography (CT) imaging of the petrous bones, which reveals the frequent bilaterality of this anatomical variation as well as the presence of associated anomalies. We report on two cases of persistent stapedial artery discovered during CT scan explorations.

Reproducibility of three-dimensional cephalometric landmarks in cone-beam and low-dose computed tomography.

OBJECTIVES: The purpose of this study is to compare the reproducibility of three-dimensional cephalometric landmarks on three-dimensional computed tomography (3D-CT) surface rendering using clinical protocols based on low-dose (35-mAs) spiral CT and cone-beam CT (I-CAT). The absorbed dose levels for radiosensitive organs in the maxillofacial region during exposure in both 3D-CT protocols were also assessed. MATERIALS AND METHODS: The study population consisted of ten human dry skulls examined with low-dose CT and cone-beam CT. Two independent observers identified 24 cephalometric anatomic landmarks at 13 sites on the 3D-CT surface renderings using both protocols, with each observer repeating the identification 1 month later. A total of 1,920 imaging measurements were performed. Thermoluminescent dosimeters were placed at six sites around the thyroid gland, the submandibular glands, and the eyes in an Alderson phantom to measure the absorbed dose levels. RESULTS: When comparing low-dose CT and cone-beam CT protocols, the cone-beam CT protocol proved to be significantly more reproducible for four of the 13 anatomical sites. There was no significant difference between the protocols for the other nine anatomical sites. Both low-dose and cone-beam CT protocols were equivalent in dose absorption to the eyes and submandibular glands. However, thyroid glands were more irradiated with low-dose CT. CONCLUSIONS: Cone-beam CT was more reproducible and procured less irradiation to the thyroid gland than low-dose CT. CLINICAL RELEVANCE: Cone-beam CT should be preferred over low-dose CT for developing three-dimensional bony cephalometric analyses.

Tips and traps in spinal cord pathology.

While reviewing major pathological conditions, the radiologist must learn to adapt his technique to the indication and look for multifocal lesions. In conditions involving malformation, transdural cord herniation and diastematomyelia may be discovered late. In vascular diseases, a dural arteriovenous fistula with perimedullary venous drainage is the most common vascular malformation and a source of diagnostic error. On discovering a medullary cavity, the radiologist needs to know when to discount focal distensions of the ependymal canal and how to detect tumoral syringomyelia. In the case of a tumour, he should know the characteristics of common tumours such as astrocytomas, ependymomas, haemangioblastomas and cavernomas. In inflammatory diseases, he should know when a brain examination is required. When faced with images appearing to show a tumour, he should consider the possibility of pseudotumours and in particular of granulomatoses.

Locked-in syndrome as an unusual complication of acute otitis media.

BACKGROUND: A 32-year-old woman developed altered consciousness two days after initial symptoms of acute otitis media, with purulent discharge from the right ear. She was quadriplegic, with spontaneous eye opening, mild neck stiffness, and lacking vestibular-ocular reflexes. METHODOLOGY: Upon admission, the patient was subjected to brain computed tomography (CT), magnetic resonance imaging (MRI), and lumbar puncture. RESULTS: CT was consistent with pansinusitis, right middle ear otitis, mastoiditis, and sphenoiditis. No brainstem lesion was evident; brain MRI demonstrated ischemic and secondary hemorrhagic lesions in the pons and cerebral peduncles. The dura mater in the petroclival space was intensely inflamed, and likely responsible for reduced basilar arterial blood flow. Lumbar puncture yielded clear cerebrospinal fluid; gram stain examination was negative and culture remained sterile. Streptococcus pneumoniae and Haemophilus influenzae were cultured from the purulent ear discharge. CONCLUSION: The final diagnosis was locked-in syndrome consecutive to inflammatory changes compressing the basilar artery.

Hemiballism revealing type 2 diabetes in an elderly: clinical and neuroimaging findings and etiopathogenic links.

Hemiballism-hemichorea is characterized by non-patterned and involuntary unilateral movements. It is a rare clinical sign unmasking type 2 diabetes mellitus, mostly in elderly patients. We report the clinical and neuroimaging findings of a patient admitted for hemiballism-hemichorea of the right upper limb, leading to the diagnosis of type 2 diabetes. We hereby describe clinical and neuroimaging findings. After initiation of treatment and restoration of euglycaemia, we note a complete remission of the initial neurological symptoms.

Extensive neurosarcoidosis and optic nerve complications.

We present the case of a 35-year-old patient suffering from nasal obstruction and headache for 3 years. The patient was hospitalized for a recent and progressive decline of vision of the right eye associated with afferent pupillary deficit and inferior altitudinal hemianopsia. He was diagnosed with systemic sarcoidosis involving the central nervous system as illustrated by magnetic resonance imaging (MRI) scans showing different type diffuse lesions of meningo-encephalitis. Our case is characterized by severe cerebral pachyleptomeningeal lesions complicated by optic nerve compression and cervical spinal cord damage. MRI value of diagnosis for systemic neurosarcoidosis was supported by histological examination of a biopsy of the sphenoid sinus lesions that showed epithelioid granulomas presence without caseous necrosis. Thus, MRI of the brain and spinal cord is a powerful tool method in monitoring and diagnosing asymptomatic and symptomatic neurosarcoiodosis. MRI is also a powerful tool in monitoring the neurosarcoidosis during therapeutic treatments.

White matter anatomy of the human deep brain revisited with high resolution DTI fibre tracking.

BACKGROUND AND PURPOSE: Deep white matter (WM) fascicles play a major, yet poorly understood, role in the overall connectivity of human brain. Better knowledge of their anatomy is requisite to understand the clinical correlates of their lesions and develop targeted treatments. We investigated whether MR-based diffusion tensor imaging (DTI) and fibre tracking could reveal in vivo, in explicit details, the 3D WM architecture within the subthalamic region and the internal capsule. METHODS: High-resolution DTI images were acquired on six healthy volunteers on a three Tesla MR scanner. We studied using single-subject analysis WM fascicles within the subthalamic region and the internal capsule, as follows: DTI deterministic fibre tracking (FT) of fascicles; embedding fascicles in the volume-rendered brain coupled with a triplanar view; rigorous anatomic labelling of each fascicle according to classical knowledge as described by pioneer neuroanatomists. Deterministic FT effects were taken into account. RESULTS: We charted most of WM fascicles of the deep brain, in particular large and complex fascicles such as the basal forebrain bundle and the ansa lenticularis. A topographic classification of subthalamic fascicles was proposed into three groups: the cerebellorubral, the reticulo-dorsal and the tegmento-peripheral one. CONCLUSIONS: Beyond to demonstrate the feasibility of imaging the deepest WM fascicles in vivo, our results pave the way for a better understanding of the brain connectivity and for developing targeted neuromodulation.

Intra-operative 3.0 T magnetic resonance imaging using a dual-independent room: long-term evaluation of time-cost, problems, and learning-curve effect.

We present a short and comprehensive report of our 39-month experience using a 3.0 T intra-operative magnetic resonance imaging (ioMRI) neurosurgical-MR twin room, including a description of the problems encountered and the associated time-delays. Forty-seven problems were experienced during the 189 ioMRI procedures (two ioMRI were performed in five of the 184 surgical procedures) performed in the 39-month period, including a blocked transfer table, failure of anesthetic monitoring material, and specific MRI-related problems, such as head and coil positioning difficulties, artefacts, coil malfunctions and other technical difficulties. None of these problems prevented the ioMRI procedure from taking place or affected image interpretation, but they sometimes caused a significant delay. Fifteen (32%) of these problems occurred during the initial learning curve period. The mean duration of the ioMRI procedure was 75 min, which decreased slightly with experience, although an average waiting-for-access time of 24 min could not be avoided. These results illustrate that although performing ioMRI at 3.0 T with the dual room is a challenging procedure, it remains safe and feasible and associated with only minor dysfunctions while offering optimal image quality and standard surgical conditions.

[Intramedullary tumours and pseudotumours]. / Moelle épinière tumorale et pseudo-tumorale.

Swelling of the spinal cord and/or enhancement after intravenous gadolinium administration are not always specific features of intramedullary tumour. These may also be seen in association with several diseases of inflammatory, infectious, granulomatous or vascular origin. A tumour is characterized by its sagittal location, axial topography: central, lateral or exophytic, its size and size of the spinal canal, macroscopic components: calcium, fat, methemoglobin, melanin, hemosiderin, vascular pedicle, cystic component, enhancement after intravenous gadolinium administration, effect on the spinal cord tracts and edema. Characteristics: astrocytoma is lateral and infiltrative, ependymoma is central with white matter tract displacement and hemosiderin cap, hemangioblastoma is postero-lateral and shows enhancement with a vascular pedicle, metastases are very edematous or leptomeningeal in location.

Reversible splenial lesion syndrome in cerebral malaria.

A 71-year-old Caucasian man living in Congo was investigated by serial magnetic resonance imaging (MRI) after having presented cerebral malaria due to Plasmodium falciparum. The clinical picture was characterized initially by coma and seizures. The patient developed multiple organ failure. There was, at 4 months follow-up only, a minimal neurological improvement consistent with minimally conscious state. The first cerebral MRI on day 17 showed a lesion of the splenium of corpus callosum with high signal intensity on DWI and FLAIR sequence and reduced ADC, and small cortical infarcts in the internal occipital regions. Follow-up MRI obtained 36 days later showed a complete resolution of splenial lesion, though without clinical improvement. Cerebral malaria should be added to the list of possible causes of reversible lesion of the splenium of corpus callosum.

Gliomatosis cerebri, imaging findings of 12 cases.

BACKGROUND AND PURPOSE: We report 12 cases of Gliomatosis cerebri (GC), a rare brain neoplasm, to define its semeiologic criteria. Literature was reviewed to clarify its physiopathology. PATIENTS AND METHODS: From 1997 to 2008, 12 histologically proven cases with GC were retrospectively reviewed. Of the 12 patients, nine were male. The mean age was of 54 years. Were performed CT-Scan (n=6), MRI (n=12), diffusion and perfusion weighted images (n=12 and n=4), MR Spectroscopy (n=3), a FDG and a Methionin PET-Scan (n=2 and n=3 respectively). RESULTS: Primary diagnosis was missed in six cases. Most frequent clinical signs were seizure and mental changes. Imaging criteria were: area of high signal intensity on FLAIR and T2-weighted images, involving three or more contiguous lobes with conserved architecture. Frequently a bilateral widespread invasion with involvment of the corpus callosum or the anterior white commissure or both was observed. At diagnosis and in the classical form (type I) of GC, no significant contrast enhancement and decreased rCBV were observed. Focal enhancement and increased rCBV were observed in the focal mass in type II GC. MR Spectroscopy showed an increase of the Cho/Cr ratio and a decrease in the NAA/Cr one. FDG PET showed in type I a decreased avidity for the FDG whereas in type II a increased avidity was observed. MET-PET showed an increased avidity for the tracer in a GC type II and a slight avidity in a GC type I. CONCLUSION: GC is a rare brain entity. Primary diagnosis is often missed. The imaging findings of GC I, a WHO grade III tumor, should be known and include classical MRI but also PWI, MRS and scintigraphic findings.

Substitution of 11C-methionine PET by perfusion MRI during the follow-up of treated high-grade gliomas: preliminary results in clinical practice.

PURPOSE: Our aim was to compare perfusion magnetic resonance imaging (MRI) and positron emission tomography (PET) using carbon-11 labelled methionine (MET) in gliomas and their value in differentiating tumour recurrence from necrosis. MATERIALS AND METHODS: We retrospectively reviewed 28 patients with a high-grade glioma. A total of 33MR perfusions and MET-PET were ultimately analysable for comparison between the relative cerebral blood volume (rCBV) and MET-PET examinations. Intra- and interobserver reproducibility was assessed and diagnostic value of rCBV compared to MET-PET and histology was assessed by the area under the receiver operating characteristic (ROC) curve. RESULTS: ROC curve analysis showed that rCBV had at least equal performances in differentiating tumour recurrence and necrosis than MET-PET. Cut-off value of rCBV for differentiating tumour from necrosis was 182% with a sensitivity of 81.5% and a specificity of 100%. CONCLUSION: In clinical practice, perfusion MRI could replace MET-PET for differentiating necrosis from tumour recurrence.

Brain death in a septic patient: possible relationship with posterior reversible encephalopathy syndrome?

A 41-year-old man with a previous kidney transplant was referred for arterial hypertension and acute renal failure. Initial neurological examination was normal. Laboratory data showed a high serum cyclosporine A concentration. A few hours later, he developed generalised tonic-clonic seizures. The brain computed tomogram was not remarkable, but Glasgow Coma Scale score remained at 8. Mechanical ventilation was required for rapidly progressive hypoxaemia related to Staphylococcus aureus pneumonia and septicaemia. Noradrenaline infusion was needed for only nine hours, with no major drop in mean arterial blood pressure. On day three his Glasgow Coma Scale score was 3/15, with fixed dilated pupils. The brain computed tomogram revealed bilateral hypodense lesions in the posterior areas together with cerebral oedema and the patient was subsequently declared brain dead. We discuss the possibility of a posterior reversible encephalopathy syndrome, likely triggered by a gram-positive septicaemia in addition to other risk factors.

[Comparison of lumbar spinal canal measurements on MRI and CT]. / Comparaison des mesures du canal lombaire en IRM et TDM.

PURPOSE: To compare AP diameter measurements of spinal canal and thecal sac on MRI and CT. MATERIALS AND METHODS: The AP diameter of the spinal canal at L4 and thecal sac at L4-5 were measured on both MRI and CT performed on patients at less than one month interval. Measurements were obtained from axial CT images of the abdomen on CT and sagittal T1W (n = 98) and T2W (n = 78) MR images of the spine. The examinations were reviewed at more than 24 hours interval. Radiologists were blinded. Inter-observer agreement evaluation was performed prior to this study. Measurements were compared using a t test for paired variables. RESULTS: For the spinal canal, mean measurements were 0.4 +/- 1.5mm inferior on CT compared to MRI. For the thecal sac, mean measurements were 0.1 +/- 1.4mm inferior on CT compared to MRI. CONCLUSION: Measurements on CT and MRI for lumbar spinal canal and thecal sac are fairly comparable, with mean measurement differences inferior to the degree of precision of the measurement technique itself.

Intraoperative 3T MR imaging for spinal cord tumor resection: feasibility, timing, and image quality using a "twin" MR-operating room suite.

We assessed feasibility, safety, and timing of an original intraoperative MR procedure in 3 cases of resection of spinal cord glioma by using a clinical 3T MR system connected to an adjacent operating room in a design being coined "twin" or "dual" MR-operating room suite.

Accuracy of three-dimensional (3D) craniofacial cephalometric landmarks on a low-dose 3D computed tomograph.

OBJECTIVES: The aim of this paper is to compare the accuracy of cephalometric landmark identification using three-dimensional CT (3D-CT) surface rendering with "high-dose" (200 mAs) and "low-dose" (35 mAs) CT protocols. The absorbed dose levels for radiosensitive organs in the maxillofacial region during the exposure for both 3D-CT protocols were also measured. METHODS: The study population consisted of 15 human dry skulls examined with spiral 3D-CT. 12 cephalometric anatomical landmarks at 7 sites were identified on the 3D-CT surface renderings by 2 observers independently, twice each, using high-dose and low-dose protocols. In total, 1440 imaging measurements were made. Thermoluminescent dosemeters (TLDs) were placed at ten sites around the thyroid and submandibular glands and the eyes in an Alderson phantom for measuring the absorbed dose levels. RESULTS: The intraobserver mean distances between 3D landmarks were smaller for all sites with the high-dose protocol (P = 0.37). There was a significant difference among the observers (P = 0.000004). Interobserver mean distances between 3D landmarks were smaller for four of the seven sites with the low-dose protocol. However, the global interobserver mean distances between 3D landmarks for all sites were smaller with the high-dose protocol (P = 0.028). The low-dose protocol reduced the radiation dose to the thyroid by 6.12, to the submandibular salivary glands by 5.91 and to the eye by 5.44, resulting in a global reduction factor of 5.71. CONCLUSIONS: The accuracy in the landmark's identification was maintained when the milliampere-second values were reduced from 200 mAs to 35 mAs. We recommend use of the low-dose protocol for clinical 3D-CT cephalometric applications.