Prevalence of Asymptomatic Middle Cranial Fossa Floor Pits and Encephaloceles on MR Imaging.

BACKGROUND AND PURPOSE: Temporal lobe encephaloceles are increasingly identified and treated as epileptogenic foci. However, there is relatively scant research on the prevalence of asymptomatic encephaloceles. This study set out to describe the frequency of incidental temporal lobe encephaloceles and middle cranial fossa pits. MATERIALS AND METHODS: A retrospective review was completed of high-resolution (≤0.5-mm section thickness) axial T2WI for internal auditory canal protocol imaging. The presence and laterality of middle cranial fossa pits (small bony defects containing CSF) and encephaloceles (brain parenchyma protrusion through osseous defects with or without bony remodeling) were recorded. Electronic medical records of patients with encephaloceles were searched for a history of seizure. RESULTS: A total of 203 patients were included in the final cohort; 106 (52.2%) women. Forty-five (22.2%) patients had middle cranial fossa pits: 14 (31.1%) unilateral on the right, 17 (37.8%) unilateral on the left, and 14 (31.1%) bilateral. Ten (5.0%) patients had ≥1 encephalocele, none of whom had a documented history of seizure in the electronic medical record. No significant difference was noted in the frequency of pits or encephaloceles based on sex (P = .332 and P = .383, respectively) or age (P = .497 and P = .914, respectively). CONCLUSIONS: Incidental middle cranial fossa pits are common findings, and their prevalence is not related to age or sex. Temporal lobe encephaloceles, though rarer, also exist occasionally among asymptomatic patients. Such findings have diagnostic implications for encephaloceles identified during imaging work-up for epilepsy.

Pilot study of radiation dose reduction for pediatric head CT in evaluation of ventricular size.

BACKGROUND AND PURPOSE: CT is a ubiquitous, efficient, and cost-effective method to evaluate pediatric ventricular size, particularly in patients with CSF shunt diversion who often need emergent imaging. We therefore sought to determine the minimum dose output or CT dose index required to produce clinically acceptable examinations. MATERIALS AND METHODS: Using a validated noise insertion method and CT projection data from 22 patients, standard pediatric head CT images were reconstructed with weighted filtered back-projection and sinogram-affirmed iterative reconstruction corresponding to routine, 25%, and 10% dose. Reconstructed images were then evaluated by 3 neuroradiologists (blinded to dose and reconstruction method) for ventricular size, diagnostic confidence, image quality, evidence of hemorrhage, and shunt tip location, and compared with the reference standard. RESULTS: There was no significant difference in the ventricular size ranking, and the sensitivity for moderate to severe hydrocephalus was 100%. There was no significant difference between the full-dose level and the ventricular size rankings at the 25% or the 10% dose level for either reconstruction kernel (P > .979). Diagnostic confidence was maintained across doses and kernel. Hemorrhage was more difficult to identify as image quality degraded as dose decreased but was still seen in a majority of cases. Shunts were identified by all readers across all doses and reconstruction methods. CONCLUSIONS: CT images having dose reductions of 90% relative to routine head CT examinations provide acceptable image quality to address the specific clinical task of evaluating ventricular size.

Stroke-like migraine attacks after radiation therapy (SMART) syndrome is not always completely reversible: a case series.

We retrospectively reviewed clinical and imaging findings in 11 patients with stroke-like migraine attacks after radiation therapy (SMART) syndrome to better understand this disorder previously thought to be reversible. Six men and 5 women had complex bouts of neurologic impairment beginning, on average, 20 years after cerebral irradiation. All had characteristic, unilateral gyriform enhancement on MR imaging that developed within 2-7 days and typically resolved in 2-5 weeks. Unlike prior reports, 45% had incomplete neurologic recovery manifesting as dysphasia, cognitive impairment, or hemiparesis. The remaining 55% recovered completely over an average of 2 months. Three of 11 patients developed cortical laminar necrosis. Brain biopsies in 4 of 11 did not demonstrate a specific pathologic substrate. These additional 11 patients contribute to the understanding of variability in stroke-like migraine attacks after radiation therapy syndrome, which often but not uniformly manifests with headaches and seizures, demonstrates a typical evolution of imaging findings, and may result in permanent neurologic and imaging sequelae.

Paraneoplastic isolated myelopathy: clinical course and neuroimaging clues.

OBJECTIVE: To report the clinical phenotype and outcome of isolated paraneoplastic myelopathy. METHODS: We systematically reviewed clinical, serologic, and MRI data for 31 patients (20 female) who presented with an isolated myelopathy and coexisting cancer: carcinoma (lung, 9; breast, 7; kidney, 2; thyroid, 2; ovary/endometrium, 2), melanoma (2), or other cancer (3), or a paraneoplastic autoantibody with strong cancer association (amphiphysin-immunoglobulin G [IgG], 9; collapsin response-mediator protein 5-IgG, 9; Purkinje-cell cytoplasmic autoantibody type 1, 2; antineuronal nuclear autoantibody [ANNA]-1, 1; ANNA-3, 1). RESULTS: Of 31 patients who presented with a progressive myelopathy, symptom onset was subacute in 16 (52%). The median age was 62 years. CSF abnormalities included elevated protein (>45 mg/dL), 22; pleocytosis, 15; excess oligoclonal bands (normal <4), 7. MRI cord abnormalities identified in 20 patients were longitudinally extensive (>3 vertebral segments), 14; symmetric tract or gray matter-specific signal abnormality, 15 (enhancing in 13). Myelopathy preceded cancer diagnosis in 18 patients (median interval 12 months; range 2-44). After myelopathy onset, 26 patients underwent oncologic treatment, immunosuppressive treatment (median delay to commencing immunotherapy 9.5 months [range 1-54]), or both; only 8 improved (31%). At last neurologic evaluation (median interval after onset 17 months; range 1-165 months), 16 patients (52%) were wheelchair-dependent (median time from onset to wheelchair 9 months [range 1-21]). Ten patients died after a median of 38 months from symptom onset (range 7-152). CONCLUSION: Symmetric, longitudinally extensive tract or gray matter-specific changes on spinal MRI should raise suspicion for a paraneoplastic myelopathy. Resulting disability is often severe. Only a minority of patients improve with treatment.

Instructive case report. A 26-year-old Indian woman with seizures and multiple intracranial mass lesions.

We describe the case of a 26-year-old Indian woman who presented to our institution with seizures and papilledema. Her diagnosis was originally thought to be neurocysticercosis, but later confirmed to be intracranial tuberculoma. Antituberculous therapy with isoniazid, rifampin, pyrazinamide and ethambutol was initiated. Improvement in the patient's neurological symptoms with diminution in size of the intracerebral lesions was observed. This case illustrates the difficulty in distinguishing intracranial tuberculoma from neurocysticercosis. Radiological features that distinguish these two diseases are described. Both diseases must be considered in regions endemic for tuberculosis and cysticercosis.

Multifocal brain MRI artifacts secondary to embolic metal fragments.

We report a patient with unusual MRI abnormalities that had the physical characteristics of ferromagnetic artifact. We believe that the MRI artifacts were due to microscopic embolic metal fragments, most likely from a mechanical heart valve prosthesis. Potential sources of metal emboli should be considered in patients with MRI abnormalities compatible with ferromagnetic artifact.

Magnetic resonance imaging in cancer-related lumbosacral plexopathy.

OBJECTIVE: To study the relative utility of computed tomography (CT) and magnetic resonance imaging (MRI) of the lumbosacral plexus in patients with systemic cancer and plexopathy. DESIGN: In a retrospective study, we identified all patients encountered at Mayo Clinic Rochester between 1987 and 1993 with a diagnosis of lumbosacral plexopathy, and we selected for analysis those with MRI scans of the plexus (an abnormal finding was not necessary for inclusion) and a clinical and electrophysiologic appearance consistent with a diagnosis of metastatic lumbosacral plexopathy. MATERIAL AND METHODS: The study group consisted of 31 patients (20 men and 11 women). The types of tumor were as follows: prostatic, 10 patients; colorectal, 7; bladder, 3; cervical, 3; and other, 8. Eighteen patients had received pelvic radiotherapy before diagnosis of lumbosacral plexopathy. All available MRI scans (in 27 patients) were reviewed blinded; the initial imaging report was used if the actual scans were unavailable (in 4). CT had been done in 22 patients, and results for 16 were available for blinded review. Original reports were available for the other six. RESULTS: Direct involvement of the lumbosacral plexus by tumor was evident on 23 MRI studies, and 6 others showed widespread metastatic disease in the region of the plexus. On 13 CT examinations, direct involvement of the lumbosacral plexus by tumor was noted. In four patients, MRI findings were abnormal and CT findings were normal. No patient had abnormal CT findings and normal MRI findings. CONCLUSION: In this retrospective review, MRI was more sensitive than CT for diagnosing cancer-induced lumbosacral plexopathy. Thus, use of MRI should be considered in the diagnostic work-up of patients with clinical and electrophysiologic evidence of plexopathy and suspected systemic cancer.

Mesial temporal sclerosis: diagnosis with fluid-attenuated inversion-recovery versus spin-echo MR imaging.

PURPOSE: To compare the accuracy of a fluid-attenuated inversion-recovery (FLAIR) sequence with that of a conventional double spin-echo (SE) sequence in the identification of increased signal intensity of the hippocampus in mesial temporal sclerosis (MTS). MATERIALS AND METHODS: Three blinded reviewers independently graded the FLAIR and SE images in 36 patients with intractable complex partial seizures. Reproducibility was tested. At histopathologic examination, the criterion standard, 32 patients had MTS. RESULTS: The accuracy of FLAIR images was 97% versus 91% for SE images (P<.02). The radiologists preferred the contrast properties of FLAIR to those of SE images by a significant margin (P<.0001). Surgical to nonsurgical hippocampal contrast-to-noise ratio (C/N) measurements were better for the second echo of the SE sequence than for FLAIR (P<.002). Hippocampus-to-background tissue C/N was superior with FLAIR (P<.0001). CONCLUSION: FLAIR provides images with T2-weighted contrast and complete suppression of high signal intensity of CSF. Incorporation of a FLAIR sequence into the routine MR evaluation of patients with epilepsy is recommended.

Diagnosis of mesial temporal sclerosis with conventional versus fast spin-echo MR imaging.

PURPOSE: To test the accuracy of fast spin-echo (FSE) imaging versus that of double-echo conventional spin-echo (CSE) imaging in identification of the increased hippocampal signal intensity associated with mesial temporal sclerosis (MTS). MATERIALS AND METHODS: Thirty-four subjects who subsequently underwent anterior temporal lobectomy for intractable seizures and in whom the presence or absence of MTS was ascertained with certainty were imaged with CSE and FSE. Three blinded reviewers evaluated the first and second CSE images (CSE1 and CSE2) and the FSE images. RESULTS: CSE1 imaging had lower accuracy than FSE (P = .038) and CSE2 (P = .006) imaging. CSE2 imaging was slightly more accurate than FSE imaging (P = .048). Contrast-to-noise ratios were lower for CSE1 imaging than for CSE2 or FSE imaging (P < .001). CONCLUSION: The FSE sequence evaluated was more time efficient than CSE imaging but slightly less accurate. Therefore, substitution of this sequence for a CSE sequence seems unwarranted.

Intractable nonlesional epilepsy of temporal lobe origin: lateralization by interictal SPECT versus MRI.

We performed a retrospective study of 53 consecutive "nonlesional" temporal lobectomy patients to assess the relative utility of MRI versus interictal single-photon emission computed tomography (SPECT) in this patient population. We compared the seizure lateralizing properties of MRI and SPECT using multiple blinded expert reviewers for both SPECT and MRI with a test-retest reviewer paradigm and measurements of hippocampal volume from MRI. The criterion standard for seizure lateralization was satisfactory postoperative seizure control (n = 43). The rate of correct seizure lateralization was significantly greater for MRI than for SPECT (p < or = 0.01), and the rate of incorrect lateralization was significantly less for MRI than for SPECT. The most accurate MRI measure was hippocampal volume measurements, which correctly lateralized the seizures in 86.0% of cases. The correct lateralization rate for SPECT was 45.4%. The MRI and SPECT studies tended to be noncomplementary with respect to seizure lateralization, and SPECT was likely to give an incorrect or indeterminate result in patients who were not lateralized by MRI. Concordant MRI-EEG lateralization was a strong predictor of satisfactory postoperative seizure control, while no relationship between postoperative seizure control and SPECT findings was present.

Invasive lobular carcinoma of the breast: mammographic findings and extent of disease at diagnosis in 184 patients.

OBJECTIVE: Invasive lobular carcinoma of the breast is a distinct malignant neoplasm consisting of small cells that tend to infiltrate in thin strands that are often only one cell in width. The objectives of this study were to determine if these tumors are more frequently overlooked on mammograms than are other types of invasive carcinoma and to evaluate the specific mammographic and pathologic findings of this disease at the time of diagnosis. MATERIALS AND METHODS: From 1983 through 1991, invasive, purely lobular carcinoma of the breast was diagnosed in 184 women who had screen-film mammography and biopsy at our institution. We examined the initial mammographic reports to determine the principal abnormal mammographic findings that supported or prompted biopsy and to distinguish abnormalities that were overlooked in breasts with false-negative mammographic findings. All mammograms were retrospectively examined for benign or suspicious microcalcification in the vicinity of the neoplasm and for breast parenchymal patterns. Surgical pathology reports were also reviewed. RESULTS: The rate of false-negative findings on initial interpretations of mammograms was 19%. Forty-six percent of the mammograms with false-negative initial interpretation showed no evidence of malignant tumor in retrospect. Ten percent of the neoplasms showed suspicious calcification on mammograms, and 1% of patients had biopsy primarily because of worrisome calcification. Invasive lobular carcinoma tends to produce masses that are of relatively low radiographic opacity, similar to normal fibroglandular breast tissue. Forty-four percent of patients had metastases to axillary lymph nodes at the time of diagnosis. One patient had bilateral invasive lobular carcinoma. CONCLUSION: Our results show that the false-negative rate for the diagnosis of invasive lobular carcinoma is higher than that for other invasive cancers. The reasons for this difference appear to be the low rate of suspicious calcification found with invasive lobular carcinoma and its tendency to be of low opacity. We also found a lower rate of bilateral invasive lobular carcinoma than has been generally reported. Metastases to lymph nodes were common at the time of diagnosis.