Amish H. Doshi

An update to the Raymond–Roy Occlusion Classification of intracranial aneurysms treated with coil embolization

Background The Raymond–Roy Occlusion Classification (RROC) is the standard for evaluating coiled aneurysms (Class I: complete obliteration; Class II: residual neck; Class III: residual aneurysm), but not all Class III aneurysms behave the same over time. Methods This is a retrospective review of 370 patients with 390 intracranial aneurysms treated with coil embolization. A Modified Raymond–Roy Classification (MRRC), in which Class IIIa designates contrast within the coil interstices and Class IIIb contrast along the aneurysm wall, was applied retrospectively. Results Class IIIa aneurysms were more likely to improve to Class I or II than Class IIIb aneurysms (83.34% vs 14.89%, p<0.001) and were also more likely than Class II to improve to Class I (52.78% vs 16.90%, p<0.001). Class IIIb aneurysms were more likely to remain incompletely occluded than Class IIIa aneurysms (85.11% vs 16.67%, p<0.001). Class IIIb aneurysms were larger with wider necks while Class IIIa aneurysms had higher packing density. Class IIIb aneurysms had a higher retreatment rate (33.87% vs 6.54%, p<0.001) and a trend toward higher subsequent rupture rate (3.23% vs 0.00%, p=0.068). Conclusions We propose the MRRC to further differentiate Class III aneurysms into those likely to progress to complete occlusion and those likely to remain incompletely occluded or to worsen. The MRRC has the potential to expand the definition of adequate coil embolization, possibly decrease procedural risk, and help endovascular neurosurgeons predict which patients need closer angiographic follow-up. These findings need to be validated in a prospective study with independent blinded angiographic grading.

Tissue-Negative Transient Ischemic Attack: Is There a Role for Perfusion MRI?

OBJECTIVE Approximately 60% of patients with a clinical transient ischemic attack (TIA) do not have DWI evidence of cerebral ischemia. The purpose of this study was to assess the added diagnostic value of perfusion MRI in the evaluation of patients with TIA who have normal DWI findings. MATERIALS AND METHODS The inclusion criteria for this retrospective study were clinical presentation of TIA at admission with a discharge diagnosis of TIA confirmed by a stroke neurologist, MRI including both DWI and perfusion-weighted imaging within 48 hours of symptom onset, and no DWI lesion. Cerebral blood flow (CBF) and time to maximum of the residue function (Tmax) maps were evaluated independently by two observers. Multivariate analysis was used to assess perfusion findings; clinical variables; age, blood pressure, clinical symptoms, diabetes (ABCD2) score; duration of TIA; and time between MRI and onset and resolution of symptoms. RESULTS Fifty-two patients (33 women, 19 men; age range, 20-95 years) met the inclusion criteria. A regional perfusion abnormality was identified on either Tmax or CBF maps of 12 of 52 (23%) patients. Seven (58%) of the patients with perfusion abnormalities had hypoperfused lesions best detected on Tmax maps; the other five had hyperperfusion best detected on CBF maps. In 11 of 12 (92%) patients with abnormal perfusion MRI findings, the regional perfusion deficit correlated with the initial neurologic deficits. Multivariable analysis revealed no significant difference in demographics, ABCD2 scores, or presentation characteristics between patients with and those without perfusion abnormalities. CONCLUSION Perfusion MRI that includes Tmax and CBF parametric maps adds diagnostic value by depicting regions with delayed perfusion or postischemic hyperperfusion in approximately one-fourth of TIA patients who have normal DWI findings.

CT of Anatomic Variants of the Paranasal Sinuses and Nasal Cavity: Poor Correlation With Radiologically Significant Rhinosinusitis but Importance in Surgical Planning

OBJECTIVE The purpose of this study was to determine the incidence of sinonasal anatomic variants and to assess their relation to sinonasal mucosal disease. MATERIALS AND METHODS A retrospective evaluation of 192 sinus CT examinations of patients with a clinical history of rhinosinusitis was conducted. The CT scans were evaluated for the presence of several anatomic variants of the sinonasal cavities, and the prevalence of each variant was calculated. Prevalences of all sinonasal anatomic variants were compared between patients who had minimal to no apparent imaging evidence of rhinosinusitis and those who had radiologic evidence of clinically significant rhinosinusitis. RESULTS The most common normal variants were nasal septal deviation, Agger nasi cells, and extension of the sphenoid sinuses into the posterior nasal septum. We found no statistically significant difference in the prevalence of any of the studied anatomic variants between patients with minimal and those with clinically significant paranasal sinus or nasal cavity disease. CONCLUSION Analysis of every routine CT scan of the paranasal sinuses obtained for sinusitis or rhinitis for the presence of different anatomic variants is of questionable value unless surgery is planned.

Neuroimaging in Central Nervous System Infections

Radiologic imaging is often employed to supplement clinical evaluation in cases of suspected central nervous system (CNS) infection. While computed tomography (CT) is superior for evaluating osseous integrity, demineralization, and erosive changes and may be more readily available at many institutions, magnetic resonance imaging (MRI) has significantly greater sensitivity for evaluating the cerebral parenchyma, cord, and marrow for early changes that have not yet reached the threshold for CT detection. For these reasons, MRI is generally superior to CT for characterizing bacterial, viral, fungal, and parasitic infections of the CNS. The typical imaging features of common and uncommon CNS infectious processes are reviewed.

Interval Change in Diffusion and Perfusion MRI Parameters for the Assessment of Pseudoprogression in Cerebral Metastases Treated With Stereotactic Radiation

OBJECTIVE Apparent increases in the size of cerebral metastases after stereotactic radiosurgery (SRS) can be caused by pseudoprogression or true disease progression, which poses a diagnostic challenge at conventional MRI. The purpose of this study was to assess whether interval change in DWI and perfusion MRI parameters can differentiate pseudoprogression from progressive disease after treatment with SRS. MATERIALS AND METHODS Patients with apparent growth of cerebral metastases after SRS treatment who underwent pre- and post-SRS DWI, dynamic susceptibility contrast (DSC)-MRI, and perfusion dynamic contrast-enhanced (DCE)-MRI were retrospectively evaluated. Final assignment of pseudoprogression or progressive disease was determined at 6-month follow-up imaging using the Response Assessment in Neuro-Oncology Brain Metastases criteria. Mean values of apparent diffusion coefficient (ADC), DCE-MRI-derived volume transfer constant (Ktrans), and DSC-MRI-derived relative cerebral blood volume (CBV) from pre- and post-SRS MRI scans were compared between groups using univariate and regression analysis. Fisher exact test was used to compare interval change of imaging biomarkers. RESULTS Of 102 cerebral metastases evaluated, 32 lesions in 29 patients met our inclusion criteria. The mean duration of follow-up was 7.2 months (range, 6-14 months). Twenty-two lesions were determined as pseudoprogression, and 10 lesions were determined as progressive disease using the Response Assessment in Neuro-Oncology Brain Metastases criteria at 6-month follow-up MRI. The interval change pattern of our imaging parameters matched the expected patterns of treatment response for ADC (23/32 lesions; 72%; p = 0.055; odds ratio, 5.1), Ktrans (24/32 lesions; 75%; p = 0.006; odds ratio, 19.2), and relative CBV (27/32 lesions; 84%; p = 0.001; odds ratio, 25.3). CONCLUSION Pseudoprogression can be distinguished from disease progression in cerebral metastases treated with SRS via an interval decrease in relative CBV and Ktrans values.

Clinical Reasoning: A 61-year-old man with conjugate gaze deviation, hemiparesis, and asymmetric reflexes

A 61-year-old man with a history of alcoholic cirrhosis was transferred from an outside hospital for spontaneous bacterial peritonitis, septic shock, and respiratory failure after intubation. The patient was initially on sedation; however, more than 48 hours after the sedative was discontinued, his mental status remained depressed and he also developed new onset of conjugate rightward gaze deviation. On neurologic examination, the patient was unresponsive to verbal stimuli and sternal rub. He could not follow any command, including closing or opening eyes and squeezing hands. He had remarkable conjugate, forced eye deviation that could not be corrected to cross the midline using the vestibulo-ocular reflex. Corneal and gag reflexes were preserved. He blinked to visual threat less on the left side, had no clear facial asymmetry, and withdrew on his right arm and knees but had a flaccid left arm. His reflexes were brisker on the left biceps and brachioradialis, and the other deep tendon reflexes were absent. His plantar reflex was upgoing on the left side and downgoing on the right side. CT of the head had no significant findings.

Pseudo-Foster-Kennedy syndrome with optic nerve compression by the gyrus rectus

A 21-year-old woman presented with headaches and left eye visual loss. Examination revealed acuity 20/20 OD and finger counting OS, a left afferent pupillary defect, papilledema OD, and optic atrophy OS. Left atrophy was unexplained until orbital MRI revealed left nerve compression by the gyrus rectus (figure, A), displaced by an intraventricular central neurocytoma (figure, B). Foster-Kennedy syndrome is characterized by optic atrophy on one side due to direct optic nerve mass lesion compression with contralateral papilledema. This case is termed pseudo-Foster-Kennedy with indirect compressive optic neuropathy due to brain displacement from a tumor distant from the optic nerve.1

Paradoxical evolution of a cerebellar tuberculosis abscess after surgical drainage and antibiotic therapy.

Background: Involvement of the central nervous system (CNS) by a tuberculosis abscess is a rare form of extra-pulmonary tuberculosis. With proper treatment, the abscess most commonly follows a pattern of continued reduction in size. Case Description: A 71-year-old male with a past medical history of kidney transplant on immunosuppressive therapy, presented to the hospital with a 1-day history of headache. On physical examination, the patient had no focal neurological symptoms. Initial laboratory reports were unremarkable. Contrast enhanced magnetic resonance imaging (MRI) was performed, which showed a ring enhancing mass and perilesional edema in the left cerebellar hemisphere. The patient underwent a left posterior fossa biopsy and drainage. The lesion was encapsulated with a purulent center. Cultures revealed pan-sensitive mycobacterium tuberculosis and the patient was started on rifampicin, isoniazid, pyrazinamide, ethambutol, and B6. The patient was monitored carefully and brain MRIs were obtained at 1, 4, 9, 11, and 14 months. It was noted that the tuberculosis abscess had grown in size from month 4 to month 9 of treatment. Since the patients neurologic examination and symptoms were stable at that time, the drug regimen was not changed. The 14-month follow up MRI showed that the abscess had nearly resolved. Conclusion: Rarely, the pattern of CNS tuberculosis abscess evolution may include growth, even with proper treatment. This pattern does not necessarily signify treatment failure, as our abscess resolved without change in treatment. Given the possibility of asymptomatic abscess enlargement, close clinical and imaging follow up are crucial in management of these cases.