AJNR Blog » CT techniques

Aunt Mickey (they look the same until you undress them). Carotid-cavernous fistula or something else?

MCastillo — Mon, 23 Nov 2009 18:06:14 +0000

A middle age woman presented with left progressive proptosis. A contrast enhanced CT was done and showed enlargement of the left superior ophthalmic vein on the axial plane (see below). A coronal image confirmed this abnormality and demonstrated that the extraocular muscles and retro-orbital fat had a normal appearance.

Physical examination showed no chemosis, vision loss or cranial nerve palsies. Because of this the patient was brought back for repeat contrast enhanced CT of the orbits with Valsalva maneuver. This study showed mild additional enlargement of the already prominent left superior ophthalmic vein and also of the right sided one (see below). The combination of imaging and clinical findings was thought to be most compatible with orbital varices. The patient opted for conservative management.

Orbital varices are hamartomas composed of slow flow, low pressure and thinned walled and distensible blood vessels. As they communicate with the rest of the circulation, they enlarge with Valsava, bending or prone position, and coughing and straining. They produce proptosis which may be painful and because they may bleed, their symptoms may become acutely exacerbated. They may also erode adjacent bone. Treatment is very difficult and is reserved for those with repeated hemorrhages, thrombosis, optic nerve compression and disfigurement. Orbital vascular processes included in the differential diagnosis are carotid cavernous fistulas of both types and less likely, venous thrombosis.

In CC fistulas, the ipsilateral cavernous sinus may be enlarged particularly in the direct ones (see below). Extra-ocular muscles may also be large and the retro-ocular fat may have a “dirty” appearance. In most patients with direct CCFs, chemosis, decreased vision and cranial nerve palsies are present. Acute thrombosis of the superior ophthalmic vein may present with symptoms that are similar to those of a direct CCF. Indirect CCFs may have less acute symptoms and be clinically similar to varices. The diagnosis is confirmed with catheter angiography as shown here.

CT head – what slice thickness do you use?

Scoffings Daniel — Thu, 12 Nov 2009 12:30:38 +0000

Until recently we have been scanning routine CT heads using a sequential technique with 5 mm slices through the posterior fossa and 10 mm slices of the supratentorial compartment. With a change of machines the protocols were revamped and we are now using sequential 5 mm thick slices all the way through.

One of my colleagues has complained about this change, stating that lesion conspicuity will be reduced by using thinner slices above the tent. I personally prefer the uniform and thinner slice thickness but cannot find anything in the literature to support either argument – there is lots about acquiring as thinly as possible in the posterior fossa but nothing regarding the optimum slice thickness for the cerebral hemispheres.

Can anybody help?

Validation and Standardization of Stroke Perfusion Methods

mlev — Thu, 05 Feb 2009 13:01:38 +0000

CTP and MRP acquisition hardware, protocols, post processing, and interpretation vary widely between centers. If we are to use these techniques for rational triage of acute stroke patients to appropriate treatment, validation and standardization is required. I encourage all who perform such imaging to participate in the “STIR” effort, being corrdinated by Max Wintermark et al at UCSF.