Embolic stroke from common carotid pseudo-aneurysm

Clinical images: A 52 year old man presented with signs of a stroke in the territory of the right middle cerebral artery. He was also found to have a large pulsatile mass at the base of his neck on the right side. Subsequent clinical imaging revealed a pseudoaneurysm (false aneurysm) of the right common carotid artery

The impact of optic nerve movement on optic nerve magnetic resonance diffusion parameters

Background: Optic nerve diffusion imaging is a useful investigational tool of optic nerve microstructure, but is limited by eye-movement-induced optic nerve movement and artifacts from surrounding cerebrospinal fluid, fat, bone and air. Attempts at improving patient cooperation, thus voluntarily limiting eye movement during a standard diffusion imagingsequence, are usually futile. The aim of this study was to establish the impact of optic nerve movement on clinical diffusion parameters of the optic nerve. Method: Twenty-nine healthy volunteers with intact vision and intact conjugate gaze were recruited and subjected to magnetic resonance diffusion-weighted imaging (DWI) and diffusion-tensor imaging (DTI) of the optic nerves. Twenty right eyes had nerve tracking done using single-shot echo-planar imaging at 20 time points over 3 minutes. Optic nerve movement measurements were correlated with diffusion parameters of apparent diffusion coefficient (ADC), mean diffusivity (MD), fractional anisotropy (FA) and anisotropic index(AI) using Spearman’s rank correlation. Results: No significant correlations were noted between optic nerve movement parameters and ADC in the axial plane and MD of the optic nerve. Low to moderate negative correlations were noted between optic nerve movement parameters and AI and FA and positive correlation with ADC in the radial plane. Conclusion: Optic nerve movement documented during the timespan of standard diffusion sequences (DWI and DTI) has a negative effect on the anisotropic diffusion parameters of the optic nerve. With greater eye movement, optic nerve diffusion appears less anisotropic owing to greater radial diffusion

Early Clinical and Subclinical Visual Evoked Potential and Humphrey's Visual Field Defects in Cryptococcal Meningitis.

Cryptococcal induced visual loss is a devastating complication in survivors of cryptococcal meningitis (CM). Early detection is paramount in prevention and treatment. Subclinical optic nerve dysfunction in CM has not hitherto been investigated by electrophysiological means. We undertook a prospective study on 90 HIV sero-positive patients with culture confirmed CM. Seventy-four patients underwent visual evoked potential (VEP) testing and 47 patients underwent Humphrey's visual field (HVF) testing. Decreased best corrected visual acuity (BCVA) was detected in 46.5% of patients. VEP was abnormal in 51/74 (68.9%) right eyes and 50/74 (67.6%) left eyes. VEP P100 latency was the main abnormality with mean latency values of 118.9 (±16.5) ms and 119.8 (±15.7) ms for the right and left eyes respectively, mildly prolonged when compared to our laboratory references of 104 (±10) ms (p<0.001). Subclinical VEP abnormality was detected in 56.5% of normal eyes and constituted mostly latency abnormality. VEP amplitude was also significantly reduced in this cohort but minimally so in the visually unimpaired. HVF was abnormal in 36/47 (76.6%) right eyes and 32/45 (71.1%) left eyes. The predominant field defect was peripheral constriction with an enlarged blind spot suggesting the greater impact by raised intracranial pressure over that of optic neuritis. Whether this was due to papilloedema or a compartment syndrome is open to further investigation. Subclinical HVF abnormalities were minimal and therefore a poor screening test for early optic nerve dysfunction. However, early optic nerve dysfunction can be detected by testing of VEP P100 latency, which may precede the onset of visual loss in CM

Frequencies of Visual Field Defects.

<p>Constricted VF – Constricted Visual Field.</p

Correlation between HVF and VA, CSF Pressure, Swollen optic disc, CD4 count and VEP in 47 patients.

<p>HVF – Humphrey's visual field, VEP – Visual evoked potential, Visual Acuity refers to Best Corrected Visual Acuity.</p

VEP latency and amplitude findings in 66 patients.

<p>VEP – Visual Evoked Potential, VA – Visual Acuity, Norm – normal, lat – latency, amp – amplitude, Abn – abnormal.</p

Correlation between VEP and VA, CSF Pressure, Swollen optic disc and CD4 count in 66 patients.

<p>VEP – Visual Evoked Potential, Visual Acuity refers to Best Corrected Visual Acuity.</p

Frequencies of Abnormal VA, VEP and HVF.

<p>N – Number, VEP – Visual Evoked Potential, HVF – Humphrey's Visual Field.</p