Nobutaka Yoshioka

Vascular anatomy of the anteriorly based pericranial flap

OBJECTIVE: The purpose of this study was to examine the vascular supply of the anteriorly based frontal pericranial flap to determine whether separating the pericranium from the galea above the orbital rim would devascularize the pericranial flap. METHODS: The arteries supplying and the veins draining the frontal pericranial flap were examined in 17 adult cadavers using ×3 to ×30 magnification. The arteries were examined on 25 sides and the veins on 16 sides. RESULTS: The main trunk and superficial branches of the supraorbital and supratrochlear arteries, which course in the galea-frontalis muscle layer, give rise to the deep branches that supply the pericranium. These pericranial branches may arise in the orbit or at the level of or above the orbital rim. Pericranial arteries that arose above the level of the orbital rim and would be divided in separating the galea and pericranium were found in 28% of the sides examined. Pericranial veins that coursed above the orbital rim and would be divided in separating the galea-frontalis muscle layer from the pericranial layer were found in 43.8% of the sides examined. CONCLUSION: In preparing a pericranial flap based anteriorly on the supraorbital rim, the separation of the galea-frontalis muscle layer from the pericranium layer should not extend into the 10 mm above the supraorbital rim if the arterial and venous pedicle of the pericranial flap is to be preserved.

One-piece versus two-piece orbitozygomatic craniotomy: quantitative and qualitative considerations.

OBJECTIVE: The orbitozygomatic (OZ) craniotomy minimizes brain retraction and improves cranial base exposure by providing a multidirectional view, increased operative angles and working space. The two main variations of the approach include the one-piece and the two-piece types. The microsurgical anatomy of the one- and two-piece OZ craniotomies are presented with the goal of comparing the extent of orbital roof removal between these two craniotomies and the effect of orbital roof removal on operative exposure. METHODS: Ten two-piece and 11 one-piece OZ craniotomies were performed in a stepwise manner simulating the approaches on formalin fixed specimens. The orbital surface area removed above the frontozygomatic suture extending medially over the orbital roof was measured from each bone flap. The two-sided unpaired t test using STATA 7.0 software was used to compare the amount of orbital roof removed using the two approaches. RESULTS: The two-piece OZ craniotomy allowed for the removal of a larger portion of the roof and lateral wall of the orbit than the one-piece. The total orbitotomy, including the orbital roof plus the part of the lateral wall above the frontozygomatic suture, had an average surface area of 996 ± 229 mm2 for the two piece and 372 ± 103 mm2 for the one-piece. The orbital roof made up 27 ± 18% of the orbital osteotomy for the one-piece craniotomies and 67 ± 10% of the osteotomy for the two-piece craniotomies (P < 0.001). CONCLUSION: The two-piece OZ craniotomy allows for more extensive orbital roof removal and better visualization of the basal frontal lobe. Therefore, the two-piece may result in a lower incidence of enophtalmus and poor cosmetic outcomes, particularly if the remaining orbital roof must be removed piecemeal during the one-piece OZ craniotomy in order to obtain satisfactory exposure.

MacCarty keyhole and inferior orbital fissure in orbitozygomatic craniotomy.

OBJECTIVE: This study had two objectives. The first was to define the ideal position of the MacCarty keyhole, a commonly used craniotomy entry site into which three of the bone cuts in orbitozygomatic craniotomy extend. The second objective was to examine the relationships in the inferior orbital fissure, a site into which two of the bone cuts in orbitozygomatic craniotomy extend. METHODS: Twenty frontotemporal regions from adult skulls were examined to delineate the relationships between the surface anatomy of the fronto-orbitozygomatic region and the underlying frontal fossa and orbit. Drill holes placed along, above, and below the frontosphenoid suture were made beginning anteriorly at an area referred to as the three-suture junction, located at the junction of the frontozygomatic, sphenozygomatic, and frontosphenoid sutures. The site of the deep end of each hole was recorded to clarify the ideal position of the keyhole. The relationships in the inferior orbital fissure, the site of the lower end of the bone cut that begins in the orbital portion of the keyhole and extends along the lateral orbital wall, were also examined. CONCLUSION: Placing the MacCarty keyhole on the frontosphenoid suture 5 to 6 mm behind the three-suture junction results in greater preservation of the lateral wall and roof of the orbit than when the hole is placed at a more anterior site, as previously recommended. The anterolateral part of the inferior orbital fissure, which faces the temporal fossa and into which the bone cuts in the orbitozygomatic craniotomy extend, has a lower density of vascular and neural structures than the middle and posteromedial parts, which are related to the infratemporal and pterygopalatine fossa.

Scalp to Meningeal Arterial Anastomosis in the Parietal Foramen

OBJECTIVE: The purpose of this study was to examine the parietal foramen and to determine whether it is the site of an anastomosis between the meningeal and scalp arteries. METHODS: Forty parietal regions from 20 adult cadavers, in which the arteries were perfused with colored latex, were examined for this study. The scalp was separated from the parietal foramen, and the vasculature in the foramen and adjacent scalp and dura were examined using ×3 magnification. The scalp arteries that anastomosed with the meningeal arteries through the parietal foramen were followed into the dura after craniotomy. RESULTS: Parietal foramen was found in 20 of the 40 (50%) parietal regions. They were present bilaterally in eight heads and unilaterally in four. Every parietal foramen transmitted an anastomosis between the middle meningeal and scalp arteries. In 11 (55%) of the 20 foramina found in this study, the superficial temporal and occipital artery formed an anastomosis in the galea and pericranial layer that sent a branch through the parietal foramen to anastomose with parietal branches of the middle meningeal artery. In the remaining nine (45%) sides, the middle meningeal artery had a connection through the foramen with a small pericranial artery. CONCLUSION: Every parietal foramen was the site of a connection between the middle meningeal and scalp arteries. The scalp end of the anastomosis most commonly arose in an anastomosis between the superficial temporal and occipital arteries. This anastomosis may be involved in several pathologies.

Differential Reanimation of the Midface and Lower Face Using the Masseteric and Hypoglossal Nerves for Facial Paralysis

BACKGROUND Hypoglossal nerve transfer is frequently employed to reanimate the paralyzed facial muscles after irreversible proximal facial nerve injury. However, it can cause significant postoperative synkinesis because it involves the reinnervation of the whole mimetic musculature using a single motor source. OBJECTIVE To describe our experience with differential reanimation of the midface and lower face using separate motor sources in patients with short-term facial paralysis after brain surgery. METHODS Seven patients underwent combined nerve transfer (the masseteric nerve to the zygomatic branch and the hypoglossal nerve to the cervicofacial division of the facial nerve) and cross-facial nerve grafting with the aim of achieving a spontaneous smile. The median duration of paralysis before surgery was 7 mo and follow-up ranged from 7 to 31 mo (mean: 18 mo). For evaluation, both physical examination and video analysis were performed. RESULTS In all patients, reanimation of both the midface and the lower face was successful. A nearly symmetrical resting lip was achieved in all patients, and they were able to voluntarily elevate the corners of their mouths without visible synkinesis and to close their eyes while biting. No patient experienced impairment of masticatory function or tongue atrophy. CONCLUSION Differential reanimation of the midface and lower face with the masseteric and hypoglossal nerves is an alternative method that helps to minimize synkinetic mass movement and morbidity at the donor site.