Temporal/Frontal Branch of Facial Nerve

Origin of Frontal/Temporal Branch

The temporal/frontal branch of the facial nerve arises from the superomedial aspect of the parotid gland.

More specifically, this branch arises from the temporofacial trunk – which forms part of the pes anserinus and is located superficial to the retromandibular vein in 90% of cases^​1​

Course of Frontal/Temporal Branch

The temporal/frontotemporal branches emerge from the superior surface of the parotid, cross the zygomatic arch and travel towards the pterion and the superolateral brow.

Pitanguy’s Line

A general guide for location of the temporal/frontal branches of facial nerve. Pitanguy’s Line in 0.5 cm inferior to the tragus to a point 1.5cm superior and lateral to the eyebrow^​2​.

Davies’ Area

This is a general guide for the distribution of the frontal/temporal branch of the facial nerve. Whilst Pitanguy’s line uses variable soft tissue landmarks, Davies in 2013^​3​ identified palpable surface features to predict the course. According to this study, the greatest distribution of frontal branch is within these following boundaries:

1. Anterior: Zygomatic suture line (ZSL) connecting zygomaticotemporal and frontozygomatic suture.
2. Inferior: Infraorbitomeatal line (IOML) connecting the infra-orbital margin and the external acoustic meatus.
3. Superior: Supra­orbitomeatal line SOML (SOML) – connecting the supra-orbital margin and the external acoustic meatus.
4. Posterior: Porion Line connecting the SOML and IOML 12mm in front of the porio (upper landmark of external acoustic meatus/superior aspect of tragus)

Depth/Layers

It is important to understand the facial nerve is not a 2-dimensional structure but rather a goes through different depths/layers in the face and skull. After leaving the superior surface of the parotid gland, the frontal/temporal branch of facial nerve^​4​:

1. Pierces the parotidomassteric fascia (White Line)
2. Cross the zygomatic arch in the subcutaneous tissue (Blue Line)
3. Enter the subgaleal space (Yellow Line

Anatomical Variations

The facial nerve has significant communicating branches, anatomical variation and cross-innervation. Six different branching patterns have been published^​3​.

The temporal branch usually divides into anterior and posterior rami soon after piercing the parotidomasseteric fascia below the zygomatic arch; there is often a middle (frontal) ramus.

Innervation of Frontal/Temporal Branch

Lower motor neuron lesions paralyse the ipsilateral frontalis muscle.
Upper motor neuron lesions preserve the frontalis, due to dual cortical representation of the forehead.

Muscles

The twigs of the frontal/temporal facial nerve branch innervates:

1. Frontalis Muscle – raises the eyebrows
2. Orbicularis Oculi Muscle – closes the eye
3. Corrugator Supercili Muscle – wrinkles forehead
4. Ear (intrinsics on lateral surface of auricle, Anterior and Superior auricular muscles)

Communication

Clinical Pearl:
These anastomoses and branches patterns explain why a division of a small branch often fails to result in the expected facial nerve weakness. There is significant overlap and cross-innervation.

There is also communication/anastomosis with:

1. Supraorbital and lacrimal branches of the ophthalmic nerve
2. Zygomaticotemporal branch of the maxillary nerve
3. Auriculotemporal branch of the mandibular nerve

References

1. 1. Westphal M. Cranial Neuroimaging and Clinical Neuroanatomy, Third Ed. Neuro-Oncology. July 2004:267-268. doi:10.1215/s1152851704200035
2. 2. Pitanguy I, Ramos A. The frontal branch of the facial nerve: the importance of its variations in face lifting. Plast Reconstr Surg. 1966;38(4):352-356. doi:10.1097/00006534-196610000-00010
3. 3. Davies J, Fattah A, Ravichandiran M, Agur A. Clinically relevant landmarks of the frontotemporal branch of the facial nerve: a three-dimensional study. Clin Anat. 2012;25(7):858-865. doi:10.1002/ca.22162
4. 4. D’Antoni AV. Gray’s Anatomy, the Anatomical Basis of Clinical Practice, Forty-First Edition, by Susan Standring, Editor-in-Chief,                        Elsevier Limited , 2016, 1,562 Pages, Hardcover, $228.99 ($171.74), ISBN: 978-0-7020-5230-9. Clin Anat. January 2016:264-265. doi:10.1002/ca.22677