23.1 History and Initial Description

The posterior auricular artery (PAA) has been used for decades in reconstructive, and ear, nose, and throat surgery, because of its arterial supply to myocutaneous and myofascial flaps. ^{1 ,​ 2} It lasted until some years ago, before this artery was used by neurosurgeons for extracranial–intracranial (ECIC) bypass surgery. ^{3 – 5}

The PAA supplies a small area behind the ear and the auricle itself. It is usually present as three to five small branches which anastomose with the superficial temporal artery (STA), but sometimes it is suitable as a donor artery for ECIC bypass surgery. In the majority, the PAA branches off the ECA just superior to the occipital artery, but in 10 to 15% cases it arises from the occipital artery after an occipitoauricular trunk (see Fig. 23‑1). It continues between the mastoid tip and auricle, and in 33 to 50% cases, it is large enough to extend to the temporoparietal region. ⁶ In these cases, it runs almost vertically toward the vertex until a mean distance of 7.5 cm from the mastoid tip. Its course at approximately 1.2 cm posterior to the external auditory meatus is ideal for a bypass, because it is located at the posterior margin of a standard craniotomy around the Sylvian point. In 1.2 to 5.7% of cases, the PAA diameter is large enough to function as a donor artery. ^{3 ,​ 6}

23.2 Indications

Sometimes the STA is not available as donor vessel for bypass surgery due to hypoplasia of the artery, sacrifice of the artery at previous craniotomy, damage of the artery during dissection, or if it has already been used for a bypass. In such cases, the PAA can be used as an alternative donor artery, if its diameter is large enough. Moreover, in case of refractory moyamoya disease with a standard ECIC bypass in situ, or in case of the need for a double-barrel bypass, the PAA can be used as an additional revascularization technique. ⁴ Cerebrovascular surgeons must be aware about a PAA when assessing the preoperative angiography of the ECA. When performing a craniotomy for moyamoya disease, knowledge about PAA anatomy may be valuable for planning proper incision and not damaging the PAA.

22.3 Key Principles

The PAA is easily identified on a lateral digital subtraction angiography (DSA), where it branches off the external carotid artery (ECA) and runs behind the EAC (see Fig. 23‑2). In about half the cases, it extends until the temporoparietal region. The diameter must be large enough (> 1 mm) to be used as a donor artery. Its almost vertical course along the temporoparietal region locates the artery at the posterior margin of the standard craniotomy around the Sylvian point. Because only the posterior part of the temporal muscle must be dissected to mobilize to PAA for an ECIC bypass, it causes less injury to the muscle.