Citations

✓ Metastatic seeding or iatrogenic implantation of numerous types of primary central nervous system tumors, typically along cerebrospinal fluid pathways, is a frequently described albeit rare phenomenon and has never been reported in association with vestibular schwannoma (VS). The authors present a case of inadvertent surgical implantation of VS into the cerebellar hemisphere during resection of a recurrent VS in the cerebellopontine angle and internal auditory canal. A 42-year-old man presented with a 2.5-cm right VS that was removed without complication via a retrosigmoid approach. Routine imaging performed 5 years later revealed a 1.5-cm recurrence of the VS that was subsequently removed by reopening the retrosigmoid craniotomy. Five years later—10 years after initial presentation—follow-up imaging revealed a 1-cm recurrence of the VS and a separate 2.2-cm tumor in the inferior cerebellar parenchyma with surrounding edema. Both tumors were removed without complication by reopening the previous retrosigmoid craniotomy. Histological evaluation of these tumors revealed features typical of VS and similar to those of the tissue obtained from the two prior resections. Given the similarities among these tumors in pathological appearance and mitotic index, the presence of the intraparenchymal cerebellar schwannoma was probably due to intraoperative iatrogenic implantation.

Object The purpose of this study was to examine the prevalence of intracranial cavernous malformations (CMs) in a large series of predominantly Caucasian patients with spinal cord CMs. The authors also studied the natural history of spinal CMs in patients who were treated nonoperatively. Methods The medical records of 67 consecutive patients (32 female and 35 male patients) in whom a spinal CM was diagnosed between 1994 and 2002 were reviewed. The patients’ mean age at presentation was 50 years (range 13–82 years). Twenty-five patients underwent resection of the lesion. Forty-two patients in whom the spinal CM was diagnosed using magnetic resonance (MR) imaging were followed expectantly. Thirty-three (49%) of 67 patients underwent both spinal and intracranial MR imaging. All available imaging studies were reviewed to determine the coexistence of an intracranial CM. Fourteen (42%) of the 33 patients with spinal CMs who underwent intracranial MR imaging harbored at least one cerebral CM in addition to the spinal lesion. Six (43%) of these 14 patients did not have a known family history of CM. Data obtained during the long-term follow-up period (mean 9.7 years, total of 319 patient-years) were available for 33 of the 42 patients with a spinal CM who did not undergo surgery. Five symptomatic lesional hemorrhages (neurological events), four of which were documented on neuroimaging studies, occurred during the follow-up period, for an overall event rate of 1.6% per patient per year. No patient experienced clinically significant neurological deficits due to recurrent hemorrhage. Conclusions As many as 40% of patients with a spinal CM may harbor a similar intracranial lesion, and approximately 40% of patients with coexisting spinal and intracranial CMs may have the nonfamilial (sporadic) form of the disease. Patients with symptomatic spinal CMs who are treated nonoperatively may have a small risk of clinically significant recurrent hemorrhage. The findings will aid in evaluation of surveillance images and in counseling of patients with spinal CMs, irrespective of family history.

Object The pathogenesis of intraneural ganglia has been a controversial issue for longer than a century. Recently the authors identified a stereotypical pattern of occurrence of peroneal and tibial intraneural ganglia, and based on an understanding of their pathogenesis provided a unifying articular explanation. Atypical features, which occasionally are observed, have offered an opportunity to verify further and expand on the authors' proposed theory. Methods Three unusual cases are presented to exemplify the dynamic features of peroneal and tibial intraneural ganglia formation. Results Two patients with a predominant deep peroneal nerve deficit shared essential anatomical findings common to peroneal intraneural ganglia: namely, 1) joint connections to the anterior portion of the superior tibiofibular joint, and 2) dissection of the cyst along the articular branch of the peroneal nerve and proximally. Magnetic resonance (MR) images obtained in these patients demonstrated some unusual findings, including the presence of a cyst within the tibial and sural nerves in the popliteal fossa region, and spontaneous regression of the cysts, which was observed on serial images obtained weeks apart. The authors identified a clinical outlier, a case that could not be understood within the context of their previously reported theory of intraneural ganglion cyst formation. Described 32 years ago, this patient had a tibial neuropathy and was found at surgery to have tibial, peroneal, and sciatic intraneural cysts without a joint connection. The authors' hypothesis about this case, based on their unified theory, was twofold: 1) the lesion was a primary tibial intraneural ganglion with proximal extension followed by sciatic cross-over and distal descent; and 2) a joint connection to the posterior aspect of the superior tibiofibular joint with a remnant cyst within the articular branch would be present, a finding that would help explain the formation of different cysts by a single mechanism. The authors proved their hypothesis by careful inspection of a recently obtained postoperative MR image. Conclusions These three cases together with data obtained from a retrospective review of the authors' clinical material and findings reported in the literature provide firm evidence for mechanisms underlying intraneural ganglia formation. Thus, expansion of the authors' unified articular theory permits understanding and elucidation of unusual presentations of intraneural cysts. Whereas an articular connection and fluid following the path of least resistance was pivotal, the authors now incorporate dynamic aspects of cyst formation due to pressure fluxes. These basic principles explain patterns of ascent, cross-over, and descent down terminal nerve branches based on articular connections, paths of diminished resistance to fluid flow within recognized anatomical compartments, and the effects of fluctuating pressure gradients.

Object The object of this study was to assess the results of unilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) for management of advanced Parkinson disease (PD). Methods A clinical series of 24 patients (mean age 71 years, range 56–80 years) with medically intractable PD, who were undergoing unilateral magnetic resonance imaging–targeted, electrophysiologically guided STN DBS, completed a battery of qualitative and quantitative outcome measures preoperatively (baseline) and postoperatively, using a modified Core Assessment Program for Intracerebral Transplantations protocol. The mean follow-up period was 9 months. Statistically significant improvement was observed in the Unified Parkinson's Disease Rating Scale (UPDRS) Part II score (18%), the total UPDRS PART III score (31%), the contralateral UPDRS Part III score (63%), and scores for axial motor features (19%), contralateral tremor (88%), rigidity (60%), bradykinesia (54%), and dyskinesia (69%), as well as the Parkinson's Disease Quality of Life questionnaire score (15%) in the on-stimulation state compared with baseline. Ipsilateral symptoms improved by approximately 15% or less. Performance on the Purdue pegboard test improved in the contralateral hand in the on-stimulation state compared with the off-stimulation state (38%, p < 0.05). The daily levodopa-equivalent dose was reduced by 21% (p = 0.018). Neuropsychological tests revealed an improvement in mental flexibility and a trend toward reduced letter fluency. There were no permanent surgical complications. Of the 16 participants with symmetrical disease, five required implantation of the DBS unit on the second side. Conclusions Unilateral STN DBS is an effective and safe treatment for selected patients with advanced PD. Unilateral STN DBS provides improvement of contralateral motor symptoms of PD as well as quality of life, reduces requirements for medication, and possibly enhances mental flexibility. This method of surgical treatment may be associated with a reduced risk and may provide an alternative to bilateral STN DBS for PD, especially in older patients or patients with asymmetry of parkinsonism.

Object The causes of epileptic events remain unclear. Much in vitro and in vivo experimental evidence suggests that gap junctions formed by connexins (Cxs) between neurons and/or astrocytes contribute to the generation and maintenance of seizures; however, few experiments have been conducted in humans, and those completed have shown controversial data. The authors designed a study to compare the level of expression of Cxs in hippocampi from epileptic and nonepileptic patients to assess whether an alteration of gap junction expression in epileptic tissue plays a role in seizure origin and propagation. Methods The expression of Cxs32, -36, and -43 was studied in 47 consecutive samples of hippocampi obtained from epileptic patients who had undergone an amygdalohippocampectomy for the treatment of intractable seizure. These expression levels were compared with those in hippocampi obtained in nonepileptic patients during postmortem dissection. Immunostaining was performed to create one slide for each of the three Cxs. Each slide demonstrated multiple cells from each of six regions (CA1, CA2, CA3, CA4, dentate gyrus, and subiculum). Two independent reviewers rated each Cx–region combination according to an immunoreactive score. Across all three measures—that is, staining intensity, percentage of positively stained cells, and immunoreactive score—Cx32 appeared to be expressed at a significantly lower level in the epileptic patients compared with controls (p < 0.001 for each measure), whereas Cx43 appeared to be expressed more among the epileptic patients (p < 0.001 for each measure). There was no evidence of any differential expression of Cx36. There was, however, regional variation within each Cx subtype. For Cx36, the staining intensity was higher in the CA2 region in the epilepsy group. Conclusions The increase in Cx43, decrease in Cx32, and preservation of Cx36 expression in hippocampi from epileptic persons could play a role in the development of seizures in patients with temporal sclerosis. Additional studies must be completed to understand this mechanism better.

✓The authors describe common modes of failure in the diagnosis and treatment of patients with peroneal intraneural ganglia. Illustrated examples correlate the modes of failure and the diagnostic or surgical errors. Understanding these pitfalls reinforces the rationale behind current treatment recommendations as outlined in the companion article. Avoiding these pitfalls will ultimately improve outcomes.

✓Tumoral calcinosis is a rare disorder that leads to diffuse calcium phosphate deposition into soft tissue and may be seen in the setting of uremia, hyperparathyroidism, or vitamin D intoxication. This lesion can produce significant local pain and can limit mobility in large joints where it tends to occur. Less commonly, it may produce neurological symptoms by compressing or encompassing adjacent neurovascular structures. Tumoral calcinosis involving nerve structures is challenging to treat, primarily because of its extensive size and propensity to infiltrate. Although surgical intervention can often provide symptomatic improvement, this lesion tends to recur in the presence of elevated calcium phosphate levels, and its management therefore requires a combined multidisciplinary surgical and medical approach. The authors describe two cases in which patients developed tumoral calcinosis producing peripheral nerve compression and discuss their respective surgical and medical management.

Object Previously the authors demonstrated that peroneal and tibial intraneural ganglia arising from the superior tibiofibular joint may occasionally extend proximally within the epineurium to reach the sciatic nerve. The dynamic nature of these cysts, dependent on intraarticular pressures, may give rise to differing clinical and imaging presentations that have remained unexplained until now. To identify the pathogenesis of these unusual cysts and to correlate their atypical magnetic resonance (MR) imaging appearance, the authors retrospectively reviewed their own experience as well as the published literature on these types of intraneural ganglia. Methods A careful review of MR images obtained in 22 patients with intraneural ganglia located about the knee region (18 peroneal and four tibial intraneural ganglia) allowed the authors to substantiate three different patterns: outer (epifascicular) epineurial (20 cases); inner (interfascicular) epineurial (one case); and combined outer and inner epineurial (one case). In these cases serial MR images allowed the investigators to track the movement of the cyst within the same layer of the epineurium. All lesions had connections to the superior tibiofibular joint. Nine patients were identified as having lesions with sciatic nerve extension. Seven patients harboring an outer epineurial cyst (six in whom the cyst involved the peroneal nerve and one in whom it involved the tibial nerve) had signs of sciatic nerve cross-over, with the cyst seen in the sciatic nerve and/or other terminal branches. In only two of these cases had the cyst previously been recognized to have sciatic nerve involvement. In contrast, in one case an inner epineurial cyst involving the tibial nerve ascended within the tibial division of the sciatic nerve and did not cross over. A single patient had a combination of both outer and inner epineurial cysts; these were easily distinguished by their distinctive imaging patterns. Conclusions This anatomical compartmentalization of intraneural cysts can be used to explain varied clinical and imaging patterns of cleavage planes for cyst formation and propagation. Compartmentalization elucidates the mechanism for cases of outer epineurial cysts in which there are primary ascent, sciatic cross-over, and descent of the lesion down terminal branches; correlates these cysts' atypical MR imaging features; and contrasts a different pattern of inner epineurial cysts in which ascent and descent occur without cross-over. The authors present data demonstrating that the dynamic phases of these intraneural ganglia frequently involve the sciatic nerve. Their imaging features are subtle and serve to explain the underrecognition and underreporting of the longitudinal extension of these cysts. Importantly, cysts extending to the sciatic nerve are still derived from the superior tibiofibular joint. Combined with the authors' previous experimental data, the current observations help the reader understand intraneural ganglia with a different, deeper degree of anatomical detail.