An unusual cause of generalised clonic tonic seizure in a 39year old female.

Clinical History

Sudden onset of generalised clonic tonic seizures (GTCS) in a previously healthy 39 year old female.

Imaging Findings

A 39year old female who suddenly developed a GTCS witnessed by her partner, was taken to the local hospital, where she had 2 further GTCS in hospital each lasting few minutes only. She had no past medical history of note, in particular no history of epilepsy. Drug history included only oral contraceptives which she has been on for several month; there was no history of explicit drug use. Clinical examination was normal. Blood tests and CT of the brain were normal.
After 24 hours of observation without further seizures, the patient was discharged with a referral to her local hospitals neurologist.
The patient attended the neurology clinic 2 weeks later, she had no further episodes of GTCS in the interval but described 3 episodes of migrating sensory numbness starting at the tips of the left fingers and migrating from the arm to the left side of the neck and face and the down to the left side of chest and abdomen; each episode lasting 10min. There was no history of motor deficit, and no headache/migraine. General and neurological examination was normal.
Due to the unusual history the patient was admitted for further investigations. MRI of the head showed a right parieto-frontal cortical tubular structure high signal on T1W, T2W, T2Flair, and DWI. MRV was performed and showed the deep cerebral veins and venous sinuses to be patent. No evidence of ischemic change/bleed and no SOL. The appearance on MRI was diagnostic of an isolated cortical vein thrombosis.

Discussion

Isolated cortical venous thrombosis is a relatively rare entity that is encountered much less commonly than dural sinus thrombosis and is more difficult to diagnose both clinically and radiologically.
Risk factors for venous sinus thrombosis can be classified as local or systemic. Local processes that alter the venous flow (eg. sinus trauma, regional infection such as that in mastoiditis, and neoplastic invasion or compression) may potentiate the development of thrombosis. Systemic causes include protein S and protein C deficiencies, a peripartum state, oral contraceptive use (as in our case), and hypercoagulable states secondary to malignancy. In as many as 25% of cases, no cause is identified.
Typical parenchymal findings are areas of focal cortical oedema or haemorrhage, which is non-specific. However, the finding of an adjacent thrombosed venous structure, is the most specific sign of this disorder. On CT images, this finding has been referred to as the "cord sign "; on MR images, it has been called the hyperintense vein sign (HVS).
The diagnosis of venous sinus thrombosis on MRI is based on the following criteria: (1) Typical signal abnormalities corresponding to the intraluminal clot on T1- and/or T2-weighted MRI (high or isosignal according to the type of sequence and stage of thrombosis (Figure 1, and 2). The MR equivalent of the cord sign can be difficult to identify, particularly during the acute stage of thrombosis when the clot tends to be isointense with brain on T1-WI and hypointense on T2-WI where it mimics a flow void. From 3 to 7 days after thrombosis, the clot becomes hyperintense on both T1- and T2-WI and is thus easier to identify.
(2) Absence of flow or partial flow void in thrombosed sinuses or veins in the presence of visible and normal flow in other veins on MR venography (Figure 3).
(3) On diffusion-weighted imaging (DWI), the HSV sign is seen in approximately 41% of cases [3] corresponding to the presence of intravascular clots in the presence or absence of cerebral tissue lesions (as in our case, figure 4). HSVdwi was always found in the presence of signal changes in thrombosed veins on either T1 or FLAIR images, which suggests that the presence of HSVdwi is not actually of complementary value for the diagnosis of CVT when T1 and FLAIR images are already obtained. However, one study by Favorel et al [3] observed that recanalization of occluded vein(s) or sinus(es) was less frequent when HSVdwi was present at the corresponding site on the initial MRI This result might be useful in some cases with initial unfavorable evolution for whom heparin continuation or early in situ thrombolysis is considered, although the rate of recanalization and/or the frequency of HSVdwi are not actually correlated to the risk of tissue lesions.
In conclusion, isolated cortical venous thrombosis may be difficult to diagnose and a high index of clinical suspicion and the appropriate use and careful analysis of sectional imaging or angiography (or both) are essential in confirming this diagnosis.

Differential Diagnosis List

Final Diagnosis

Cortical vein thrombosis.

URL:	https://eurorad.org/case/6973
DOI:	10.1594/EURORAD/CASE.6973
ISSN:	1563-4086