Seyed Ali Nabavizadeh

Neuroimaging in Central Nervous System Lymphoma

Primary central nervous system lymphoma (PCNSL) is a rare aggressive high-grade type of extranodal lymphoma. PCNSL can have a variable imaging appearance and can mimic other brain disorders such as encephalitis, demyelination, and stroke. In addition to PCNSL, the CNS can be secondarily involved by systemic lymphoma. Computed tomography and conventional MRI are the initial imaging modalities to evaluate these lesions. Recently, however, advanced MRI techniques are more often used in an effort to narrow the differential diagnosis and potentially inform diagnostic and therapeutic decisions.

Primary atypical optic nerve sheath meningioma in a child with restricted diffusion on magnetic resonance imaging.

Optic nerve sheath meningioma is most often discovered in adults and is relatively rare in children. We report a 12-year-old girl with an atypical primary optic nerve meningioma, which demonstrated restricted diffusion on magnetic resonance imaging and high Ki67 labeling index. The patient developed recurrence, despite aggressive surgical resection of primary tumor and local radiation. We are unaware of previous reports documenting this constellation of imaging and histopathologic findings.

The Many Faces of Cerebral Developmental Venous Anomaly and Its Mimicks: Spectrum of Imaging Findings.

Developmental venous anomalies (DVAs) are the most common cerebral vascular malformations and are usually found incidentally on neuroimaging studies. Despite the benign nature of DVAs, occasionally, they can be symptomatic. The objective of this article is to review the spectrum of imaging findings of DVAs on conventional and advanced imaging studies. In addition, neuroimaging findings of symptomatic DVAs as well as imaging mimicks will also be described to assist in the approach to differential diagnosis.

Wallerian Degeneration Beyond the Corticospinal Tracts: Conventional and Advanced MRI Findings

Wallerian degeneration (WD) is defined as progressive anterograde disintegration of axons and accompanying demyelination after an injury to the proximal axon or cell body. Since the 1980s and 1990s, conventional magnetic resonance imaging (MRI) sequences have been shown to be sensitive to changes of WD in the subacute to chronic phases. More recently, advanced MRI techniques, such as diffusion‐weighted imaging (DWI) and diffusion tensor imaging (DTI), have demonstrated some of earliest changes attributed to acute WD, typically on the order of days. In addition, there is increasing evidence on the value of advanced MRI techniques in providing important prognostic information related to WD. This article reviews the utility of conventional and advanced MRI techniques for assessing WD, by focusing not only on the corticospinal tract but also other neural tracts less commonly thought of, including corticopontocerebellar tract, dentate‐rubro‐olivary pathway, posterior column of the spinal cord, corpus callosum, limbic circuit, and optic pathway. The basic anatomy of these neural pathways will be discussed, followed by a comprehensive review of existing literature supported by instructive clinical examples. The goal of this review is for readers to become more familiar with both conventional and advanced MRI findings of WD involving important neural pathways, as well as to illustrate increasing utility of advanced MRI techniques in providing important prognostic information for various pathologies.

Temporal patterns of 18F‐fluorodeoxyglucose positron emission tomography/computed tomography sinonasal uptake after treatment of sinonasal malignancy

Current guidelines have identified 10 to 12 weeks posttreatment as the ideal time‐point for improved diagnostic accuracy of positron emission tomography/computed tomography (PET/CT) for deep tissue sites of the head and neck. After treatment, the sinonasal skull base is predisposed to prolonged inflammation that may render this time‐point inappropriate for initial posttreatment imaging surveillance for sinonasal malignancies. The purpose of this study is to evaluate temporal trends in 18F‐fluorodeoxyglucose (18FDG) sinonasal uptake after treatment for sinonasal malignancies to better elucidate the optimal time‐point for initial PET/CT posttreatment evaluation in this patient population.

Neuroimaging in Leukemia.

Leukemias are a heterogeneous group of hematologic malignancies that results from uncontrolled neoplastic proliferation of undifferentiated or partially differentiated hematopoietic cells. Patients with acute leukemia can have a variety of craniocerebral complications, which can result from direct leukemic involvement, secondary to cerebrovascular or infectious complications of leukemia, or can be treatment related. Imaging plays a central role in evaluating the central nervous system during treatment in patients with leukemia. CT scan is usually considered an effective initial imaging modality to evaluate for cerebrovascular complications. MRI is considered the imaging modality of choice due to its versatility.

Clinical manifestations and imaging findings of thrombosis of developmental venous anomalies

AIM To determine clinical manifestations, imaging findings and outcome of patients with thrombosed developmental venous anomalies (DVAs). MATERIALS AND METHODS The radiology database was searched retrospectively for thrombosed DVAs between 01/01/2000 to 07/01/2016. Demographic variables, associated risk factors, clinical manifestations, imaging findings, treatments, and follow-up were recorded. RESULTS Six patients were found (four female and two male; age range 16-45 years with mean age, 21.3 years). The most common clinical presentation was headaches followed by neurological deficits and seizures. Venous infarction, parenchymal haemorrhage, venous congestive oedema were noted as the radiological findings. Clinical outcome was favourable in all patients with complete recovery or persistence of mild neurological symptoms. CONCLUSION Thrombosed DVAs may occur under rare circumstances, which lead to variable symptoms. Familiarity with this entity and early recognition of associated findings including venous infarction, parenchymal haemorrhage, and venous congestive oedema would help early diagnosis and prompt treatment.

Non–Squamous Cell Causes of Cervical Lymphadenopathy

Cervical lymphadenopathy is a common indication for imaging evaluation of the neck. Besides metastatic squamous cell carcinoma of the head and neck, cervical lymphadenopathy can be due to many causes, with simple reactive lymphadenopathy on one end of the spectrum and malignant lymphadenopathy due to a distant infraclavicular primary, on the other end. A systematic approach to the cause of cervical lymphadenopathy, which includes pattern of lymph node enlargement, lymph node characteristics, systemic symptoms, and extranodal abnormalities, can be very useful in arriving at the correct diagnosis. In this article, various patterns of cervical lymphadenopathy due to non-squamous cell causes are discussed.

18FDG PET/CT in Routine Surveillance of Asymptomatic Patients following Treatment of Sinonasal Neoplasms

Objective Sinonasal neoplasms have a high rate of recurrence following treatment, and current guidelines support the use of a variety of surveillance techniques. Recent work demonstrates that performance parameters of surveillance modalities may differ with sinonasal tumors in particular when compared with head and neck tumors overall. This study aims to characterize the value of 18fluorodeoxyglucose (18FDG) positron emission tomography/computed tomography (PET/CT) as a screening tool in asymptomatic patients. Study Design Retrospective cohort study. Setting Hospital of the University of Pennsylvania and Pennsylvania hospital. Methods Records of asymptomatic patients without suspicious endoscopy or suspicious imaging other than PET during the first 3 years following definitive treatment for sinonasal malignancy were screened and analyzed for inclusion in the cohort. Disease recurrence was determined by biopsy following suspicious PET evaluation. Results PET/CT scans (n = 111) were performed for 45 disease-free asymptomatic patients with no evidence of disease on endoscopy, and 6.3% were suspicious and prompted biopsy during this period, revealing 3 cases of disease recurrence. Overall specificity for PET/CT alone was 96.3% (95% CI, 90.7%-99.0%), with a negative predictive value of 99% (95% CI, 94.8%-100%). All recurrences were detected between 7 and 12 months, and all patients with true recurrence diagnosed by PET/CT had extrasinonasal involvement of tumor at the time of surgery. Conclusion We examined performance parameters of 18FDG PET/CT in asymptomatic patients with no evidence of disease on endoscopy during the posttreatment period for sinonasal malignancy. The ability of PET/CT to detect recurrences that may be missed by structural imaging or endoscopy makes it a valuable tool for clinicians.

Emerging PET/MRI applications in neuroradiology and neuroscience

PET and MRI are powerful imaging techniques that have been used extensively to study diseases of the brain, head, and neck. In many diseases, including dementia, epilepsy and head and neck cancers, PET and MRI play important and complementary roles in standard diagnostic evaluation. Recent advances in PET detector technology have allowed combination of PET and MRI into a single machine capable of simultaneous imaging which may offer several, distinct advantages over serial imaging and post-acquisition fusion such as decreased patient burden and improved PET imaging quantification. In addition, a PET/MR instrument potentially has the unique ability to combine time-dependent physiological and functional information from MRI with the specific metabolic and receptor specific information from PET imaging. Over the past several years, numerous anecdotal reports and several larger studies showed the feasibility of PET/MR in various brain and head and neck applications including, for example, concomitant fMRI and PET neuroreceptor imaging. Future well-designed studies with a focus on evaluating and optimizing the synergistic qualities of these combined technologies may fulfill the promise of PET-MRI to provide unparalleled opportunities to understand complex brain function and pathology.