Carotidynia (Transient Perivascular Inflammation of the Carotid Artery)
Carotidynia is a painful carotid artery syndrome that is also known as Fay syndrome or Transient Perivascular Inflammation of the Carotid artery (TIPIC). TIPIC has a predilection for the carotid bifurcation of the external and internal carotid arteries. Several ocular manifestations have been reported in association with TIPIC.
Epidemiology of TPIC
The exact prevalence of TPIC is unknown. A prevalence of 2.8% in patients with acute neck pain was reported in one series. Another case series reported a median age of presentation in the fourth and fifth decade with a 1.5 to 1 female to male ratio.
The precise pathophysiology of TPIC remains ill-defined. TPIC typically presents with clinical and radiographic findings of vascular and perivascular inflammation at the level of the carotid bifurcation. Interestingly, TPIC does not typically narrow the diameter of the carotid lumen. This preservation of a normal blood flow in patients with TPIC supports the recent argument that carotidynia is a distinct inflammatory process of the pericarotid sheath.  The 1988 International Headache Society (IHS) classification of carotidynia includes the following features:
1.Pain, swelling or increased pulsation on applying pressure
2.Exclusion of structural causes of carotid pain
3.Neuralgia of head and neck with self-resolution in less than 14 days
4.Pain on one side of the neck with possible radiation to the head
Some authors have argued that carotidynia should be considered a 'nonvalidated entity' because the HIS (1988) criteria are not completely sensitive or specific for the diagnosis and there is no biomarker or defined antemortem histopathologic findings. The radiographic findings of thickened carotid arterial wall and infiltration of the perivascular fat suggest that the term TIPIC may be preferable to carotidynia.
The risk factors and etiology of TPIC are not known but some cases have been associated with high altitude exposure. Other rare cases followed certain medications (e.g., anti-cancer chemotherapy) but a single unifying mechanism has remained elusive in TPIC. [10, 11]
Patients with TPIC are usually middle age, presenting with unilateral neck pain in the region of the carotid bifurcation. The pain typically tends to be dull and throbbing in nature, continuous, and usually localized over the carotid bifurcation, although it may radiate to the ipsilateral mandibular, buccal, ocular, or auricular regions and is usually associated with tenderness on palpation in the region of the affected area (usually around the level of the carotid bifurcation). The pain is often worse with head or neck movements, chewing, yawning, coughing, or swallowing. Increased pulsations may also be noted in the associated carotid artery. Although TPIC is typically unilateral, bilateral cases have been reported.
Although TPIC is most recognizable by pain in the region of the carotid bifurcation, TPIC can also present with ophthalmic manifestations. The throbbing pain associated with TPIC can radiate to various areas adjacent to the carotid bifurcation, including the eye. Cassone et al. reported right-sided neck pain that radiated to the right face and eye. Color-Doppler ultrasonography and a cranial, cervical, and thoracic MRI confirmed TPIC. Horner syndrome, Adie tonic pupil, ptosis, and sluggish pupil reactions have also been reported in TPIC. 
The diagnosis of TPIC requires imaging evidence of pericarotid inflammation and should also be performed to exclude of other vascular (e.g., carotid dissection) and nonvascular (e.g., neoplasm) causes of carotidynia. Ultrasound of neck may show hypo echoic thickening, mild luminal narrowing, and carotid wall outward extension in tenderness region. Computed tomography (CT), MRI, and PET may also show characteristic adventitial thickening, enhancement, and inflammatory changes in TPIC.
Management and Prognosis
TPIC is usually self-limited, lasting 7 to 14 days but may be treated with non-steroidal anti-inflammatory drugs (NSAIDs) or corticosteroids. Although most patients with TPIC recover completely, some may experience a relapse.
Carotid dissection and giant cell arteritis are two major differential diagnoses of lateral neck pain. Other differential diagnoses would be cervical lymphadenitis, head and neck tumors, submandibular gland diseases, jugular vein thrombosis, and infections. 
Clinicians should be aware of the ophthalmic and non-ophthalmic presentations of TPIC. Neck imaging might confirm characteristic features. Treatment with anti inflammatory agents may speed recovery but the prognosis is generally good.
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- Lecler A, Obadia M, Savatovsky J, Picard H, Charbonneau F, Menjot de Champfleur,N, Naggara O, Carsin B, Amor-Sahli M, Cottier JP, Bensoussan J, Auffray Calvier E, Varoquaux A, De Gaalon S, Calazel C, Nasr N, Volle G, Jianu DC, Gout O, Bonneville F, Sadik JC. TIPIC Syndrome: Beyond the Myth of Carotidynia, a New Distinct Unclassified Entity. AJNR Am J Neuroradiol. 2017 Jul;38(7):1391-1398
- Woo JK, Jhamb A, Heran MK et-al. Resolution of existing intimal plaque in a patient with carotidynia. AJNR Am J Neuroradiol. 2008;29 (4): 732-3. doi:10.3174/ajnr.A0939 - Pubmed
- Burton BS, Syms MJ, Petermann GW et-al. MR imaging of patients with carotidynia. AJNR Am J Neuroradiol. 2000;21 (4): 766-9. Pubmed
- Sabbagh MA, De Lott LB, Trobe JD. Causes of Horner Syndrome: A Study of 318 Patients. J Neuroophthalmol. 2020 Sep;40(3):362-369. [PubMed]