Kesserwani Hassan
Neurology, Flowers Medical Group, Dothan, USA.
Cureus. 2021 May 30;13(5):e15340. doi: 10.7759/cureus.15340. eCollection 2021 May.
The dynamics of increased intracranial pressure (ICP) and sixth cranial nerve palsy has undergone a paradigm shift, with emphasis shifting from a length hypothesis to a theory based on novel anatomic findings pertaining to the geometry of Dorello's canal. In particular, the sixth cranial nerve resides in a transfixed coaxial cylinder within the canal. The cisternal portion of the nerve is intradural and the rest of the nerve is extradural; therefore, with increased ICP, the former is stretched, thereby pulling on the rest of the nerve, which is anchored in Dorello's canal. We present a case of pseudotumor cerebri secondary to minocycline presenting with an isolated sixth nerve palsy. This case is used as a platform to segue into the recent findings outlined above, in particular, the evolutionary transformation of Dorello's canal from a circular outline with a bony roof to an elliptic profile with a fibro-osseus roof during hominid basocranial expansion. The fibro-osseus roof, being elastic, is particularly susceptible to the influence of raised ICP, thereby narrowing the canal and injuring the sixth cranial nerve.
颅内压（ICP）升高与第六颅神经麻痹的动态变化经历了范式转变，重点已从长度假说转向基于与多雷洛管几何形状相关的新解剖学发现的理论。特别是，第六颅神经位于该管内一个固定的同轴圆柱体内。神经的脑池部分位于硬膜内，其余部分位于硬膜外；因此，随着ICP升高，前者被拉伸，从而牵拉固定在多雷洛管内的神经其余部分。我们报告一例继发于米诺环素的假性脑瘤病例，表现为孤立性第六神经麻痹。该病例被用作一个平台，引入上述最新发现，特别是在人类基底颅骨扩张过程中，多雷洛管从具有骨性顶盖的圆形轮廓演变为具有纤维骨性顶盖的椭圆形轮廓。纤维骨性顶盖具有弹性，特别容易受到ICP升高的影响，从而使管腔变窄并损伤第六颅神经。
