The subarcuate fossa of the petrosal bone houses the petrosal lobule of the cerebellar paraflocculus. Although the subarcuate fossa can be extensive, little is known about its relative size and distribution in primates. Studies indicate parafloccular involvement with cerebellar areas coordinating vestibular, visual, auditory, and locomotor systems. Hypotheses have proposed a role for the paraflocculus in vestibular-oculomotor integration, caudal muscle control, autonomic function, and visual-manual predation. This study examines the morphology and relative extent of the subarcuate fossa/petrosal lobule in a range of living primates. Methods include study of postmortem specimens representing nine mammalian orders, and qualification of the volume of the subarcuate fossa and endocranial cavity in 155 dry primate crania of 36 genera. Results show that, in mammals, the size and morphology of the petrosal lobule is directly related to that of the subarcuate fossa. Craniometric analysis shows that the ratio of subarcuate fossa volume to endocranial volume is largest in lemuriforms. The largest ratio is in Microcebus and Hapalemur. Lorisids show a significant reduction in the size of the subarcuate fossa to almost 50% below the lemuriform mean. Tarsius is near the lemuriform mean. Among platyrrhines, the ratio is high, but significantly reduced compared to lemuiforms. The highest platyrrhine ratio is seen in Ateles, the lowest in Saimiri and Alouatta. Atelids are significantly elevated compared to cebids. In cercopithecids, the fossa is significantly reduced compared to platyrrhines. The trend toward reduction of the cercopithecid fossa is most pronounced in Theropithecus and least evident in Presbytis. In hominoids, the fossa is present only in Hylobates. In great apes and humans, other than Gorilla, the petromastoid canal occupies a similar location to the subarcuate fossa of other primates, but is not homologous to it. Neither the subarcuate fossa nor the petromastoid canal are present in Gorilla. A graded reduction of the subarcuate fossa/petrosal lobule is evident among primates which evolved later in time. The relative size of this cerebellar lobule within primates may reflect size-related factors and/or degree of neocortical evolution as these relate to usage of a specific sensory-mediated locomotor behavior. The subarcuate fossa may serve as an indicator to the differentiation of the petrosal lobule of the paraflocculus in fossil forms.
Traditional middle fossa landmarks, such as the facial hiatus and arcuate eminence, are often unreliable. This study was performed to establish an external reference from which to identify precisely the surgical anatomy of the middle fossa. The head of the malleus was identified from the middle fossa in the temporal bones of 20 adults. The lateral cortex of the temporal squamosa at the zygomatic root was used as the external plane of reference. The head of the malleus was consistently located 18 mm medial to the outer cortex on a line perpendicular to the reference plane. Medial extension of this line through the malleus head bisected the internal auditory canal. We recommend this method to precisely locate the malleus head as the first landmark in the middle fossa. Other structures, such as the geniculate ganglion, internal auditory canal, and superior semicircular canal can then be safely identified. We also present our results using this technique in six consecutive patients undergoing middle fossa surgery during the past 12 months.
This study analyzes the complications encountered in the surgical treatment of 17 patients with large glomus jugulare tumors. All 17 patients sustained either new cranial nerve palsies or exacerbation of preexisting palsies. These involved, in descending order of frequency, the facial nerve, the vagus and glossopharyngeal nerves, and the hypoglossal nerve. Postoperative palsies of the facial nerve involved 17 patients, as compared to 5 preoperatively. Fifteen patients had postoperative partial or complete paralysis of the vagus nerve as compared to eight preoperatively. Ten patients had postoperative palsies of the hypoglossal nerve as compared to six preoperatively. Other complications included CSF leak, meningitis, and wound infection. Aspiration and dysphagia were encountered postoperatively in 13 patients. Teflon injection of paretic vocal cords and cricopharyngeal myotomy effectively improved the ability to swallow and the quality of the voice. Prompt recognition and treatment of complications is essential for effective surgical management of large glomus jugulare tumors.
\s=b\This study investigates the afferent and efferent pathways by which respiratory neurons in the brain can monitor and regulate middle ear aeration. Experiments were performed on 11 adult cynomolgus monkeys (Macaca fascicularis). The neural tracer, horseradish peroxidase, was placed on the transected nerves of the tympanic plexus in four animals. Horseradish peroxidase\p=n-\labelednerve terminal fields were observed in the ipsilateral respiratory subnuclei of the nucleus of the solitary tract. This may represent the sensory pathway by which the degree of middle ear aeration is monitored by the brain. Horseradish peroxidase was injected into the eustachian tube muscles in six of the monkeys, and horseradish peroxidase\p=n-\labeledmotoneurons were observed in the ipsilateral trigeminal motor nucleus (tensor palati muscle) and nucleus ambiguus (levator palati muscle). These brain-stem motor nuclei may represent the efferent pathways by which the degree of middle ear aeration is regulated. The results of these primate experiments confirm our earlier studies on rabbits and cats. A theory for the neural control of middle ear aeration is proposed.(Arch Otolaryngol Head Neck Surg 1987;113:133-137) The control of middle ear aeration is unknown. While periodic open¬ ing of the eustachian tube is thought to maintain the air in the middle ear NY 10029 (Dr Eden). and mastoid air cells at atmospheric pressure, the exact physiology of the eustachian tube is unclear.'-2 Further¬ more, the precise composition and partial pressures of the gases in the middle ear remain uncertain.3 There is no reliable clinical test of tubai function, even though adequate mid¬ dle ear aeration is universally recog¬ nized as the key to successful surgery for chronic ear disease.1-2 Otitis media is a disease that is partly attributable to inadequate mid¬ dle ear aeration. It is the most fre¬ quent diagnosis made in children in the United States"; over 75% of chil¬ dren will manifest otitis media by the age of 5 years. The overall prevalence of otitis media is about 15% to 20%, with a peak prevalence rate between 6 to 36 months of age. The cost of health care for otitis media in the United States, including myringotomy and adenoidectomy, is estimated at $2 billion annually.4 Past research into mechanisms underlying the pathogenesis of otitis media has concentrated almost exclu¬ sively on two major themes: the ana¬ tomical and mechanical factors that may affect eustachian tube function,5 7 and the inflammatory and immuno¬ logie mechanisms of the mucosa of the middle ear and eustachian tube.810 However, even in combination, these factors do not account fully for the prevalence and natural history of oti¬ tis media. Other unexplained manifes¬ tations of prolonged underaeration of the middle ear include intractable atelectasis of the tympanic mem¬ brane, cholesteatoma formation, and the failure of tympanoplasty due to vacuumlike retraction of the newly grafted tympanic membrane.11 This lack of knowledge about the control of middle ear aeration is most ...
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