Protein S deficiency manifesting with cerebral arterial and venous thrombosis in a young female with Kissing Carotids phenomenon
Authors: Ssemmanda Salvatore , Ssekamwa Douglas , Kahendeke Carol 
Published: October 2023

Background
The term “kissing carotids” refers to an anatomical variation of the cervical carotid arteries, showing tortuosity, kinking, or coiling that come in proximity at the midline. Majority of people with kissing carotids are asymptomatic. Less than 1% of the general population have Protein S Deficiency, a type of thrombophilia associated with both cerebral venous and arterial thromboembolism. We report about a 29 year old housewife with co-existent Protein S deficiency and kissing carotids who presented with sequential thrombosis in both arterial and venous cerebral circulation systems. We discuss potential mechanisms of arterial thrombosis in Protein S deficiency and medical options for secondary stroke prophylaxis in this context.
Case Presentation
A 29-year-old HIV negative right handed housewife and mother of 3 with no documented chronic illnesses or medication presented to our institution with left hemiparesis and dysarthria of sudden onset, within a day of domestic trauma from her husband from which she sustained blunt injury to the left side of her neck. She reported no headaches or history of convulsion at presentation and was otherwise constitutionally well. Index Brain MRI revealed acute non-hemorrhagic infarcts in the right middle cerebral artery territory. Index brain MRA of cerebral vessels revealed abrupt cut off of the M1 segment of the right MCA with absent flow in its distal course and its branches suggestive of arterial thrombosis. Additionally, the extracranial cervical portions of her bilateral internal carotid arteries were noted to be approximating each other close to their origin, suggestive of kissing carotids. There was no evidence of carotid dissection on imaging of her cerebral vessels. Interval imaging of her brain and cerebral vasculature on day 4 of admission for new complaints of hallucinations and a convulsion revealed left transverse venous sinus cut off suspicious for left transverse cerebral venous sinus thrombosis and no other radiological changes from her initial imaging. Laboratory workup confirmed low Protein S activity of only 18% (normal reference range of 55–123 for non-pregnant females). In view of her Protein S deficiency and clinical presentation with both cerebral arterial and venous thrombosis, she was started on rivaroxaban for lifelong secondary arterial stroke prophylaxis. At first outpatient review 6 weeks after hospital discharge, she had normal sensorium and ambulated independently with moderate circumduction of her left lower limb.
Conclusions
We report the first described case to our knowledge, of a young female with co-existent Protein S deficiency and kissing carotids phenomenon, clinically presenting with thrombosis in both cerebral arterial and venous circulation systems. We discuss potential mechanisms of arterial thrombosis in Protein S deficiency and note that warfarin may not be a preferred option for secondary arterial stroke prophylaxis in patients with Protein S deficiency. Further studies are needed to determine the pathogenicity of hypercoagulability disorders like Protein S deficiency for arterial stroke and to guide secondary stroke prophylaxis of patients with arterial ischemic stroke in the context of hypercoagulability disorders.