Table 2.

Differential diagnosis table for carotid pseudoaneurysm.

Diagnosis	Clinical features	Ultrasound findings	CT findings	MRI findings	Angiography/DSA findings
Carotid Pseudoaneurysm	Blunt force/penetrating injury, neck haematoma/swelling, oropharyngeal swelling, stroke/TIA/cranial nerve deficits	Colour Doppler Ultrasound: “to and fro” waveform, variable echogenicity, extraluminal pattern of blood flow	CT Neck: high attenuation material adjacent to the pseudo aneurysm CTA Carotid: Contrast material enhanced pseudoaneurysm sac, bowing of the normal anatomy, abnormality of the normal vascular lumen of the carotid artery	MRI/MRA Carotid: may demonstrate intramural thrombus formation, allows assessment of the pseudoaneurysm sac size and detection of extramural haemosiderin deposition, indicative of previous haemorrhage/ extravasation. Please see Imaging findings section of the text for details on dating haemorrhage	Formal Angiography/DSA: Saccular pseudoaneurysm, assessment of diameter, feeding vessels/distal vessels, narrowing of the ICA/ECA, active extravasation
Carotid Artery Dissection	History of neck trauma or sudden shearing force to neck, post endarterectomy, TIA/stroke/carotid occlusion	Ultrasound: may demonstrate absent internal carotid artery flow in high grade stenosis, biphasic flow in the carotid bulb, high resistance flow pattern in the ipsilateral ICA or evidence of collateral flow across the Circle of Willis on transcranial Doppler ultrasound	CT brain/neck(unenhanced): may demonstrate cerebral infarction/ischaemia or hyper attenuating focus in the upper ICA indicative of extramural haematoma CTA: may demonstrate abnormal vessel contour, narrowed eccentric lumen surrounded by present shaped mural thrombus, intimal flap, dissecting aneurysm	MRI: (T1 fat saturation/T2weighted imaging) High signal crescent sign in the wall of the artery, absent blood flow, cerebral ischaemia, abnormal vessel contour on MRA/ maximum intensity projection (MIP)	Formal angiography/DSA: abnormalities of the vessel wall, string sign, string and pearl sign, pseudo aneurysm formation
Carotid Artery Aneurysm	Post blunt force injury to neck/mycotic aneurysm/post instrumentation, pulsatile swelling/mass, embolic phenomena/TIA/Stroke. Rupture - rapidly expanding neck mass	Ultrasound: irregular widening of the carotid artery with an adjacent mixed-echoic oval lesion indicative of the aneurysmal sac, with turbulent flow demonstrated in the aneurysmal artery, with or without thrombosis/partial thrombosis of the aneurysmal sac	CT brain/neck (unenhanced): evidence of stroke/cerebral ischaemia, saccular/calcified mass adjacent/contiguous with the carotid indicative of aneurysmal sac, useful in the detection of haemorrhage CTA: aneurysmal dilatation of the carotid artery (either secular or fusiform enlargement), with or without evidence of mural thrombus. 3D CT reformats allow better anatomical localisation and peri-operative planning	MRI: Dilation of the vessel lumen with hyperattenuation of the artery. Low signal mural thrombus may be present. Coronal MIP images taken from TOF vascular imaging demonstrate the fusiform/saccular dilation of the vascular anatomy	Formal angiography/DSA: demonstrate the exact size, anatomy, location, orientation of the aneurysmal dilatation. Allows visualisation of the feeding vessels and the distal vasculature precisely
Carotid blowout syndrome/Carotid artery rupture	Post instrumentation/ trauma in patient with underlying mural defect in the carotid artery, presents with rapid exsanguination and swelling of the neck, TIA/Stroke/Death if not treated immediately	Ultrasound: Extraluminal pattern of blood flow on Doppler imaging	CT brain/neck (unenhanced): evidence of neck mass adjacent to carotid indicative of haemorrhage, may be features of cerebral ischaemia/infarction CTA: contrast extravasation into the soft tissues surrounding the carotid/tracking of contrast inferiorly into the mediastinum	MRI: not recommended in the acute setting, evidence of blood products around the carotid dated as per the imaging findings section of the text	Formal angiography/DSA: rupture of the carotid artery and active extravasation of contrast
Neck haematoma	May result from any of the above aetiologies, post trauma to the carotid or a branch vessel, may be asymptomatic if small. If large may cause compressive effects on the carotid artery resulting in stroke, or the Internal jugular vein resulting in venous /occlusion/infarction or airway compromise	Ultrasound: dependent on the age of haematoma; acute haematoma: liquid/hypoechoic mass in the neck adjacent to the carotid artery	CT brain/neck (unenhanced): evidence of neck mass adjacent to carotid indicative of haemorrhage with or without associated mass effect CTA: may demonstrate active extravasation into the neck tissues	MRI: dependent on the age of haemorrhage, may be used to assess and date age of blood products as outlined in the Imaging findings section of the text	Formal angiography/DSA: may locate active arterial bleed/source of haemorrhage
Carotid Body tumour/Glomus tumour/Chemodectoma	Present as a mass in the neck resulting in unilateral paralysis of the tongue, tinnitus, globus sensation, in many instances are incidentally discovered on imaging for other clinical indications	Ultrasound: hypoechoic/weakly echogenic neck mass adjacent to the carotid vessels. Doppler imaging demonstrates increased vascularity within the lesion	CT brain/neck (unenhanced): soft tissue density, bright, early enhancement, splaying of the ICA and ECA CTA: bright, early enhancement of lesion with splaying of the carotid artery	MRI: T1: Iso/hypointense to muscle signal, “salt and pepper” appearance, intense enhancement following gadolinium enhancement	Formal angiography/DSA: splaying of the carotid vessels, lyre sign, ascending pharyngeal artery is main vascular supply
Branchial cleft cyst	Congenital defect of branchial cleft development in utero, present with transilluminable lateral neck mass, may present with abscess or infection	Ultrasound: sharply demarcated, posterior acoustic enhancement (70%), imperceptible cyst walls, variable echogenicity (anechoic 41%)	CT brain/neck (unenhanced): sharply circumscribed, well demarcated cystic structure, thin wall, fluid density inside cyst, “tail-sign” extension of the cyst wall between the ECA and ICA	MRI: T1: Variable signal, T2: hyperintense, T1 + contrast: no enhancement	not applicable
Carotid Jugular AV fistula	Post trauma to the neck, particularly where there is trauma to the carotid, post carotid artery aneurysm or carotid blowout syndrome. May present with tinnitus, headache, vertigo, cranial nerve deficits or venous haemorrhage	Ultrasound: Doppler signal with anterograde flow from carotid artery to internal jugular vein or branch vessel, high velocity turbulent flow within the fistula and an arterialised waveform within the Internal jugular vein, can provide haemodynamic information regarding fistula (e.g. velocity)	CT brain/neck (unenhanced): dilation of the internal jugular vein CTA: will demonstrate contrast flowing from the carotid artery in the arterial phase of the scan into the internal jugular vein (early appearance of contrast in the vein in the arterial phase)	MRI: FLAIR MR imaging may reveal venous congestion in the cerebral parenchyma, MRA demonstrates arteriovenous shunting with early gadolinium enhancement in the internal jugular vein in the arterial phase	Formal angiography/D SA: arteriovenous shunting with a dilated tortuous, arterialised vein
Lymphoma	Presents with unilateral enlarged neck mass along classical cervical lymph node groups, may present as multifocal lymphadenopathy, B symptoms; drenching night sweats, weight loss, cachexia. May also involve paratracheal nodal groups	Ultrasound: well defined, hypo echoic/hyperechoic mass, with occasional central necrotic region which appears ill defined/echo lucent, hilar and peripheral doppler signal indicative of hilar and peripheral vascularity. Nodal vascularity can be used as a conjugate measure of response to systemic treatment.	CT brain/neck: demonstrates a solid/cystic mass lesion; the mainstay imaging modality, used for staging disease (using the Lugano classification), provides descriptive information regarding tumour bulk, lymph node diameter, FDG PET CT (fusion imaging) used to assess response to treatment.	MRI: used in the assessment of CNS lymphoma for determination of extent/anatomy of disease distribution. Head and neck lymphomas demonstrate low signal attenuation on T1 imaging/low to high intensity on T2 weighted imaging/low enhancement following gadolinium administration	not applicable
Neurogenic tumours	May present with compressive symptoms in the neck, e.g. radiculopathy, localised pain, or may invade into bony structures resulting in architectural compromise. May be incidentally discovered on imaging performed for another indication.	Ultrasound: well-defined, ovoid or round hypoechoic mass, in association with neural tissue/nerves, occasional loculation/cystic changes, rare vascularity	CT brain/neck: mass lesion, well circumscribed, adjacent to/contiguous with nerve tissue with low level contrast enhancement (reflects the predominance of Antoni B components), cystic components most specific for Antoni A type, occasional low-density material within the centre of the mass (20–30 HU) vs higher density at the periphery (60–70 HU)	MRI: Homogenous, isointense signal to muscle on T1 imaging, T2 weighted imaging demonstrated peripheral high intensity and central relatively low intensity, occasional “target sign” on T1 imaging post gadolinium demonstrating central high intensity by focal enhancement and peripheral low intensity	not applicable
Reactive lymphadenopathy	May present with prodromal viral or bacterial illness, may be unofficial or multifocal, may be suppurative in the case of tuberculosis or pyogenic bacteria strains. May present with compressive symptoms associated with mass effect. May coalesce to form an organised collection require percutaneous drainage.	Ultrasound: hypoechoic, echogenic hilus, predominant hilar vascularity, short axis–to–long axis ratio [S/L] < 0.5 (except submandibular and parotid groups), when the ratio is > 0.5 there is high probability of sinister aetiology. Max limit for axial diameter of normal and reactive nodes is 9 mm for subdigastric and submandibular nodes and 8 mm for all other neck nodal groups. Loss of fatty hilum, focal necrosis, cystic change with necrosis are independent predictors of non-reactive aetiology.	CT brain/neck (unenhanced): demonstrated by ill-defined mass in one or more of the lymph node areas of the neck, either a discrete mass 10–15mm in diameter, or, multiple nodes 6–15mm in diameter. Occasional necrotic/suppurative nodal disease dependent on aetiology. May have associated neck fascial/ retropharyngeal space abscess, particularly, if associated with inoculation/infection following penetrating injury	MRI: T1 weighted imaging demonstrates intermediate nodal intensity, high T2 signal intensity in reactive/inflamed nodes, strong post contrast enhancement is seen, and occasional rim enhancement is specific for suppurative lymphadenitis	not applicable