The trigeminal nerve and ganglion: an anatomical, histological, and radiological study addressing the transtrigeminal approach.
BACKGROUND
The transtrigeminal route with splitting of the trigeminal ganglion (TG) is a skull base approach used to expose the posteromedial part of the cavernous sinus (CS), the base of the TG, and the petrolingual ligament (PLL).


METHODS
To verify the transtrigeminal approach (TTA), the 3 divisions of the trigeminal nerve (TN), the so-called TG, and the trigeminal root were analyzed anatomically, histologically, and radiologically. The anatomic study was performed bilaterally in 5 cadaveric head specimens. For the histologic study, 6 TN specimens removed from cadavers were used. In addition, the radiologic demonstration of the TN and its so-called ganglion was performed on 5 cases by magnetic resonance imaging (MRI) scan.


RESULTS
The TN is composed of linear, crossing, and connecting rootlets. These 3 types of rootlets indicate a plexiform constitution rather than a ganglion even though there are ganglionic cells. Consequently, the term "trigeminal plexus" may be preferred to describe this network. In our new proposed classification, the segments of the TN can be divided into 6 portions according to their relationship with the brainstem, the cisterns, and the bone structures. The first 3 segments before separating into 3 divisions are (1) pontine, (2) cisternal (preganglionic or preplexal), (3) gasserian (ganglionic or plexal). The last 3 segments after the division are (4) preforamino-fissural (postganglionic or postplexal), (5) foramino-fissural, and (6) extracranial (postforamino-fissural). A loose connective tissue along the rootlets of the maxillary and the mandibular divisions of the TN at the gasserian (ganglionic or plexal) segment enabled us to split the so-called "trigeminal ganglion" or "gasserian ganglion" to perform the TTA.


CONCLUSIONS
The TTA is possible, useful, and necessary in selected cases with invasion of the posteromedial part of the CS.
Ziyal
Ibrahim M
IM
Department of Neurosurgery, Hacettepe University, School of Medicine, Istanbul, Turkey.
Sekhar
Laligam N
LN
Ozgen
Tunçalp
T
Söylemezoğlu
Figen
F
Alper
Murat
M
Beşer
Mahmut
M
D006801:Humans; D008279:Magnetic Resonance Imaging; D019635:Neurosurgical Procedures / Q000379:methods*; D011859:Radiography; D012668:Trigeminal Ganglion / Q000033:anatomy & histology / Q000166:cytology / Q000000981:diagnostic imaging; D014276:Trigeminal Nerve / Q000033:anatomy & histology / Q000166:cytology / Q000000981:diagnostic imaging