Case: A 48 years old female patient, previously healthy, presented with right hemiparesis which improved rapidly over two days with some residual weakness. She was found to have left perforator infarct on CT, and a doppler study showed absence of bilateral ICA flow.

Fig1: CECT (actually source image of CTA) showing left gangliocapsular infarct

CT Angiogram was done which confirmed bilateral ICA occlusion.

Fig 2: CTA; 3D color SSD images; AP and oblique views; both internal carotids are completely occluded – right one from origin while on the left side a small stump is seen, right vertebral artery is dominat, left vertebral artery is hypoplastic, entire brain in almost dependent upon a solitary vessel –right vertebral, patent circle of Willis saving the patient from any major catastrophe with supratentorial parenchyma being supplied via posterior and anterior communicating arteries.

Discussion:

Spontaneous ICA dissection is an uncommon but increasingly recognized entity, with the increased awareness among physicians and the advent of modern imaging technologies, especially USG (and doppler) which is fast, ubiquitous and cheap.

Cervicocephalic dissections may occur spontaneously or secondary trauma which may be major but many patients have only minor trauma, something like playing cricket, yogasana, hiccups etc, while many housewives don't exactly recollect even trivial injuries. In some patients, they are associated with an underlying arteriopathy like

• Fibromuscular dysplasia, vessel tortuosity , Marfan syndrome , Ehlers-Danlos syndrome, Alpha-1-antitrypsin deficiency, Cystic medial necrosis, Type 1 collagen point mutation, Other connective tissue disorders
• In many, no cause of spontaneous dissection is found.
• systemic infections, hypertension,  elevated homocysteine, alcohol, OCP have also been associated..

The cervical internal carotid artery is affected in 75% of patients (usually approximately 2 cm distal to the bifurcation) and the extracranial vertebral artery in 15%. The remaining cases usually involve the intracranial internal carotid artery, intracranial vertebral artery, middle cerebral artery, or basilar artery. Anterior cerebral arteries have been traditionally considered resistant, however modern imaging esp. DSA has found dissections in them too.

15% of cases are bilateral, and one half of these occur in patients with underlying fibromuscular dysplasia.

Age/Sex: Females> males, young- middle aged; cervicocephalic dissections are responsible for 1-2.5% of ischemic strokes in the general population and for 5-20% of strokes in individuals younger than 45 years.

Clinical features: commonest-focal unilateral headache; common- focal cerebral ischemic symptoms, oculosympathetic paresis, bruits, light-headedness, and neck pain; less common- syncope, amaurosis fugax, scalp tenderness, swelling in the neck, and dysgeusia

*Cephalic pain is frequent and often inaugural in carotid dissection; its recognition is important for early diagnosis and treatment, many also have painful Horner’s syndorme.

Cerebral ischemia occurs in at least 75% of reported cases (TIAs in 30%, infarcts in 45-50%).

Imaging: fat sat axial T1WI on MR very well show the dissected artery with hematoma and thrombus

Puppy sign in bilateral ICA dissection

 J Neurol Neurosurg Psychiatry2007;78:1055 doi:10.1136/jnnp.2007.115857

However, sometimes MRI, MRA and Doppler will miss the dissections, and DSA is still the best for diagnosing as well as planning treatment.

Further reading:

1. Mokri Bahram et al. Spontaneous dissection of the cervical internal carotid artery. Annals of Neurology. http://dx.doi.org/10.1002/ana.410190204
   
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3. Lucas C, Moulin T, Deplanque D, Tatu L, Chavot D. Stroke patterns of internal carotid artery dissection in 40 patients. Stroke 1998;29: 2646-8. [PubMed]
4. Bradley Scott Townend, Laura Traves, Denis Crimmins, Bilateral spontaneous carotid artery dissection, Journal of Clinical Neuroscience, Volume 12, Issue 5, June 2005, Pages 592-594, ISSN 0967-5868, DOI: 10.1016/j.jocn.2004.08.020. (http://www.sciencedirect.com/science/article/B6WHP-4G1PKN8-8/2/c30c4ff302aaca48e64cc69e26ee967e)