John Persing, John A. Jane Jr., and John A. Jane Sr.
Robert M. Starke, John A. Jane Jr., Ashok R. Asthagiri, and John A. Jane Sr.
John A. Jane Jr., Mark D. Krieger, and John Persing
Davis G. Taylor, Panagiotis Mastorakos, John A. Jane Jr., and Edward H. Oldfield
A subset of patients with Chiari I malformation demonstrate patent subarachnoid spaces around the cerebellum, indicating that reduced posterior fossa volume alone does not account for tonsillar descent. The authors distinguish two subsets of Chiari I malformation patients based on the degree of “posterior fossa crowdedness” on MRI.
Two of the coauthors independently reviewed the preoperative MR images of 49 patients with Chiari I malformation and categorized the posterior fossa as “spacious” or “crowded.” Volumetric analysis of posterior fossa structures was then performed using open-source DICOM software. The preoperative clinical and imaging features of the two groups were compared.
The posterior fossae of 25 patients were classified as spacious and 20 as crowded by both readers; 4 were incongruent. The volumes of the posterior fossa compartment, posterior fossa tissue, and hindbrain (posterior fossa tissue including herniated tonsils) were statistically similar between the patients with spacious and crowed subtypes (p = 0.33, p = 0.17, p = 0.20, respectively). However, patients in the spacious and crowded subtypes demonstrated significant differences in the ratios of posterior fossa tissue to compartment volumes as well as hindbrain to compartment volumes (p = 0.001 and p = 0.0004, respectively). The average age at surgery was 29.2 ± 19.3 years (mean ± SD) and 21.9 ± 14.9 years for spacious and crowded subtypes, respectively (p = 0.08). Syringomyelia was more prevalent in the crowded subtype (50% vs 28%, p = 0.11).
The authors' study identifies two subtypes of Chiari I malformation, crowded and spacious, that can be distinguished by MRI appearance without volumetric analysis. Earlier age at surgery and presence of syringomyelia are more common in the crowded subtype. The presence of the spacious subtype suggests that crowdedness alone cannot explain the pathogenesis of Chiari I malformation in many patients, supporting the need for further investigation.
Paul J. Schmitt and John A. Jane Jr.
The history of endoscopic third ventriculostomy (ETV) demonstrates the importance of studying neurosurgery's history. A story that began with numerous technological advancements started to fizzle as neurosurgeons were stymied by problems encountered during the infancy of the technology they were still developing. The new technique, although sound in theory, failed to deliver a realistic solution for managing hydrocephalus; it lost the battle to the valved shunt. Over the last 15–20 years, a clearer understanding of pathophysiological mechanisms underlying various forms of hydrocephalus, along with effective implementation of evidence-based practice, has allowed for optimization of patient selection and a remarkable improvement in ETV success rates. Neurosurgeons would be wise to take the lessons learned in modernizing the ETV procedure and reassure themselves that these lessons do not apply to other methods that are tempting to dismiss as antiquated or archaic.
Davis G. Taylor and John A. Jane Jr.
Davis G. Taylor, John A. Jane Jr., and Edward H. Oldfield
Extracapsular resection of pituitary microadenomas improves remission rates, but the application of pseudocapsular techniques for macroadenomas has not been well described. In larger tumors, the extremely thin, compressed normal gland or its complete absence along the tumor’s anterior surface limits the application of the traditional pseudocapsular technique that can be used for microadenomas. However, in the authors’ experience, the interface between the pseudocapsule at the posterior margin of the adenoma and the compressed normal gland behind it is universally present, providing a surgical dissection plane. In mid-2010, the authors began using a new surgical technique to identify and use this interface for the resection of larger macroadenomas, a technique that can be used with the microscope or the endoscope.
The authors performed a cohort study using prospectively collected preoperative imaging reports and operative details and retrospectively reviewed postoperative images and clinical follow-up of patients with a pituitary macroadenoma 20–40 mm in maximum diameter undergoing microscopic transsphenoidal resection. Since dissection of the tumor capsule only pertains to encapsulated tumor within the sella and not to tumor invading the cavernous sinus, assessment of tumor removal of noninvasive tumors emphasized the entire tumor, while that of invasive tumors emphasized the intrasellar component only. The incidence of residual tumor on postoperative imaging, new-onset endocrinopathy, and recovery of preoperative pituitary deficits was compared between patients who underwent surgery before (Group A) and after (Group B) implementation of the new technique.
There were 34 consecutive patients in Group A and 74 consecutive patients in Group B. Tumors in 18 (53%) Group A and 40 (54%) Group B patients had no evidence of cavernous sinus invasion on MRI. Use of the posterior pseudocapsule technique reduced the incidence of intrasellar residual tumor on postoperative MRI for tumors without cavernous sinus invasion (39% [Group A] vs 10%, p < 0.05) and in all tumors regardless of invasion (50% vs 18%, p < 0.005). The incidence of new endocrinopathy was less likely (25% vs 12%, p = 0.098) and the recovery of prior deficits more likely (13% vs 27%, p = 0.199) among patients treated using the pseudocapsule approach, although the differences are not statistically significant.
Use of the posterior pseudocapsule dissection plane can enhance the resection of pituitary macroadenomas.
Lucia Schwyzer, Robert M. Starke, John A. Jane Jr., and Edward H. Oldfield
Correlation between tumor volume and hormone levels in individual patients would permit calculation of the fraction of tumor removed by surgery, by measuring postoperative hormone levels. The goals of this study were to examine the relationship between tumor volume, growth hormone (GH), and insulin-like growth factor–1 (IGF-1) levels, and to assess the correlation between percent tumor removal and the reduction in plasma GH and IGF-1 in patients with acromegaly.
The 3D region of interest–based volumetric method was used to measure tumor volume via MRI before and after surgery in 11 patients with GH-secreting adenomas. The volume of residual tumor as a fraction of preoperative tumor volume was correlated with GH levels before and after surgery. Examination of this potential correlation required selection of patients with acromegaly who 1) had incomplete tumor removal, 2) had precise measurements of initial and residual tumor, and 3) were not on medical therapy.
Densely granulated tumors produced more peripheral GH per mass of tumor than sparsely granulated tumors (p = 0.04). There was a correlation between GH and IGF-1 levels (p = 0.001). Although there was no close correlation between tumor size and peripheral GH levels, after normalizing each tumor to its own plasma GH level and tumor volume, a comparison of percent tumor resection with percent drop in plasma GH yielded a high correlation coefficient (p = 0.006).
Densely granulated somatotropinomas produce more GH per mass of tumor than do sparsely granulated tumors. Each GH-secreting tumor has its own intrinsic level of GH production per mass of tumor, which is homogeneous over the tumor mass, and which varies greatly between tumors. In most patients the fraction of a GH-secreting tumor removed by surgery can be accurately estimated by simply comparing plasma GH levels after surgery to those before surgery.
John A. Jane Jr., Mark D. Krieger, and Alan R. Cohen
Winson S. Ho and John A. Jane Jr.
Osteogenesis imperfecta (OI) is an inherited connective tissue disorder that causes bone fragility and deformity. Neurological manifestations, including macrocephaly and hydrocephalus, have been reported. Increased vascular fragility or bleeding diathesis also predisposes OI patients to intracranial hemorrhage. The development of chronic subdural fluid collections or hydrocephalus may require CSF diversion. The authors report a previously unrecognized complication of CSF diversion in a patient with OI, that is, a delayed severe cranial deformity, presumably due to over-shunting. In addition to the cosmetic concern, the deformity caused severe headaches and tenderness. The patient underwent craniectomy and titanium mesh cranioplasty, which resulted in the complete resolution of symptoms. This report raises the possibility that over-shunting in patients with OI could predispose to the formation of cranial deformity requiring surgical intervention.