Meybodi AT, Deng H, Benet A, Lawton MT. Intracranial-Intracranial Bypass: Rationale, Indications, and Technical Considerations. Contemp Neurosurg. 2018;40(4).
This review article outlines the indications for a cerebral revascularization procedure and patient selection considerations for cerebral bypass. The main indication to bypass can be determined before surgery using physiologic testing, including a balloon test occlusion (BTO) of the parent artery. This technique is especially useful for the internal carotid artery (ICA) but may also be applicable to other main vessels. The vessel in question is typically occluded endovascularly with a balloon for about 20 minutes. The patient is monitored for any neurologic deficit. Occurrence of a neurologic deficit with balloon occlusion alone warrants a high-flow bypass. On the other hand, if no deficit occurs with balloon occlusion, the patient’s blood pressure is lowered 20 mm Hg or 25% from baseline, whichever is greater. Emergence of a neurologic deficit after lowering the blood pressure shows that occlusion of the vessel requires a backup with a low-flow bypass. If the patient passes both phases of the BTO (occlusion and hypotensive challenge), then a bypass may not be necessary despite pathologic occlusion of the artery.
The IC-IC bypass has several advantages compared with the EC-IC bypass techniques. High-flow EC-IC bypasses require a separate neck incision to expose the donor artery. In IC-IC bypass, the donor and recipient arteries are close to each other and no additional exposure is needed, which makes the IC-IC bypass preferable regarding esthetic results. The IC-IC bypass is entirely contained within the boundaries of the cranium and protected by it, whereas the extracranial donor and interposition graft lie superficially to the cranium subject to trauma and complications related to superficial compression. Caliber match between the donor and recipient is generally best when using an IC-IC bypass. The result is a higher patency rate and fewer complications related to the anastomosis site.
The IC-IC bypass requires advanced technical skill and has a steep learning curve. The deeper corridor of the intracranial anastomosis amid perforating vessels and cranial nerves sets a more challenging surgical landscape for bypass.
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Therriault J, Ng KP, Pascoal TA, et al. Anosognosia predicts default mode network hypometabolism and clinical progression to dementia. Neurology. 2018;90(11): e932-e939. doi:10.1212/WNL.0000000000005120.
Anosognosia, a syndrome characterized by a lack of awareness of one’s illness, is commonly observed in Alzheimer disease (AD). Patients with AD with anosognosia are unaware of their cognitive deficits and the difficulties they face when performing activities of daily living. Anosognosia is also correlated with dementia severity in Alzheimer disease. Therefore, anosognosia constitutes an important clinical characteristic of patients with AD.
The study aimed to characterize the associations of anosognosia and Alzheimer disease biomarkers based on the recently described amyloid/tau/neurodegeneration construct in MCI, using [18F]florbetapir, CSF phosphorylated tau (p-tau), and [18F]FDG, respectively. The authors examine the predictive effect of anosognosia on disease progression and changes in brain glucose metabolism at a 24-month follow-up. Because anosognosia occurs frequently in the symptomatic phase of AD, they also hypothesized that anosognosia is related to an increase in neuropathologic features of AD at baseline, and correspondingly to higher rates of diagnostic conversion at 24-month follow-up. The finding of a significant relationship between anosognosia, AD biomarkers, and disease progression would support a framework where assessments of illness awareness constitute an important role in the clinical management of MCI.
They stratified 468 patients with amnestic mild cognitive impairment into intact and impaired awareness groups, determined by the discrepancy between the patient and the informant score on the Everyday Cognition questionnaire. Voxel-based linear regression models evaluated the associations between self-awareness status and baseline β-amyloid load, measured by [18F] florbetapir, and the relationships between awareness status and regional brain glucose metabolism measured by [18F]fluorodeoxyglucose at baseline and at 24-month follow-up.
The authors found that participants with impaired awareness had lower [18F]fluorodeoxyglucose uptake and increased [18F]florbetapir uptake in the posterior cingulate cortex at baseline. In addition, impaired awareness in mild cognitive impairment predicted [18F]fluorodeoxyglucose hypometabolism in the posterior cingulate cortex, left basal forebrain, bilateral medial temporal lobes, and right lateral temporal lobe over 24 months. Participants with impaired awareness had a nearly 3-fold increase in likelihood of conversion to dementia within a 2-year time frame. They conclude that anosognosia is linked to Alzheimer disease pathophysiology in vulnerable structures, and predicts subsequent hypometabolism in the default mode network, accompanied by an increased risk of progression to dementia.
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Formo M, Halvorsen CM, Dahlberg D, et al. Minimally Invasive Microsurgical Resection of Primary, Intradural Spinal Tumors is Feasible and Safe: A Consecutive Series of 83 Patients. Neurosurgery. 2018;82(3):365-371. doi:10.1093/neuros/nyx253.
The authors report on the feasibility and safety of minimally invasive surgery (MIS) for primary intradural spinal tumors. Medical charts of 83 consecutive patients treated with MIS for intradural spinal tumors were reviewed. Patients were followed up during the study year, 2015, by either routine history/physical examination or by telephone consultation, with a focus on tumor status and surgery-related complications.
There were 49 schwannomas, 18 meningiomas, 10 ependymomas, 2 hemangioblastomas, 1 neurofibroma, 1 paraganglioma, 1 epidermoid cyst, and 1 hemangiopericytoma. The surgical mortality was 0%. In 87% of cases, gross total resection was achieved. The complication rate was 11%, including 2 cerebrospinal fluid leakages, 1 asymptomatic pseudomeningocele, 2 superficial surgical site infections, 1 sinus vein thrombosis, and 4 cases of neurological deterioration. There were no postoperative hematomas, and no cases of deep vein thrombosis or pulmonary embolism.
The rate of GTR following open surgery for intradural, extramedullary tumors is reported in the range of 64%-98%, whereas the corresponding rate for intramedullary tumors is much lower. The rate of GTR following MIS for intradural, extramedullary tumors is reported to be in the range of 68%-100%. In the current study, GTR was achieved in 87% of cases. It appears that MIS provides sufficient access to most intraspinal tumors, such that they can be resected as radically with MIS as with open surgery.
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Ramirez-Zamora A, Ostrem JL. Globus Pallidus Interna or Subthalamic Nucleus Deep Brain Stimulation for Parkinson Disease. JAMA Neurol. 2018;75(3):367. doi:10.1001/jamaneurol.2017.4321.
Deep brain stimulation (DBS) is an established treatment option for management of medically refractory motor fluctuations and is more effective than the best medical therapy in improving motor function, quality of life, and on-time (periods of adequate control of PD symptoms) without troublesome dyskinesia. Appropriate selection of suitable candidates is critical for successful outcomes and generally fulfills the following criteria: diagnosis of idiopathic PD with sustained and robust response to levodopa and substantial motor disability, absence of significant dementia or unstable neuropsychiatric symptoms, absence of considerable surgical and medical risk factors, and realistic expectations. Determination of the single best surgical target for DBS remains inconclusive despite extensive research in the area.
Currently, 2 main structures are primarily targeted to treat motor complications in PD: the globus pallidus interna (GPi) and the subthalamic nucleus (STN).
To date there have been 4 large randomized clinical trials comparing the effect of both targets in advanced PD. These studies include the National Institutes of Health COMPARE trial, the Veterans Affairs (VA) Cooperative Study, the study by Anderson et al, and The Netherlands Subthalamic and Pallidal Stimulation (NSTAPS) trial. These studies included a combined 502 patients with a mean follow-up of 21 months. Overall, motor benefit in the on-stimulation state and quality-of-life measurements were similar between targets across studies.
Both targets provide a successful effect on treatment of dyskinesia and improving quality of life. However, globus pallidus interna stimulation may be preferred in patients with severe or brittle dyskinesia because it greatly reduces dyskinesia and some patients might still experience dyskinesia after subthalamic nucleus DBS.
Deep brain stimulation of the subthalamic nucleus is advantageous if one of the main goals is dopaminergic medication reduction. In patients with significant concerns about cognitive decline or mood changes, particularly regarding processing speed and working memory, GPi stimulation rather than subthalamic nucleus stimulation can be considered. In patients with prominent gait impairment, axial symptoms, or falls, GPi DBS may be preferable. The GPi and subthalamic nucleus targets complement each other within the spectrum of therapeutic options in patients with PD.
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Choi W-S, Kim J-S, Hur J-W, Seong J-H. Minimally Invasive Transforaminal Lumbar Interbody Fusion Using Banana-Shaped and Straight Cages: Radiological and Clinical Results from a Prospective Randomized Clinical Trial. Neurosurgery. 2018;82(3):289-298. doi:10.1093/neuros/nyx212.
The authors compared the radiological and clinical outcomes of unilateral minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) using 2 types of cages.
All candidates for single-level MIS-TLIF were randomized into banana-shaped cage and straight-cage groups. Plain radiographs and computed tomography scans were used for assessment of cage positions, fusion status, disc height, segmental lordotic angle, cage subsidence, and pelvic parameters. Clinical outcome was assessed using visual analog scale and Oswestry Disability Index scores.
Forty-four and 40 consecutive patients were operated on using banana-shaped and straight cages, respectively. Cage position was more anterior and lateral in the straight cage group and more medial and posterior in the banana-shaped cage group. Solid fusion was achieved in 95.2% and 96.6% of the 2 groups, respectively, at 12 mo. The change in disc height and segmental lordotic angle postoperatively was significantly greater in the banana-shaped cage group. The incidence of subsidence during follow-up was significantly higher in the banana-shaped cage group.
The stability of the fused segment is dependent largely on the location, position, and surface area of the interbody cage. The rates of reoperation, pseudoarthrosis, development of adjacent segment pathology, and clinical recurrence of symptoms are influenced by the stability of the fusion segment. The interbody cage is more important in MIS-TLIF, which features a narrower working field, asymmetric approach, and less area for posterolateral fusion.
Contrary to the author’s expectations, straight cages had significantly better coverage of the anterior portions of the endplates as well as posterior portions, with a p-value approaching significance. Coverage of the lateral position was slightly higher in the banana-shaped cage group, albeit not significantly so. These results imply that banana-shaped cages tended to be placed mostly centrally (medial position) and laterally, while straight cages tended to cover broader regions of the endplates spanning the anterior and posterior portions more evenly. Because the middle part was the weakest part of the endplate, these results might explain why the endplate violation and subsidence rate was higher in the banana-shaped cage group.
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Mariette X, Criswell LA. Primary Sjögren’s Syndrome. Solomon CG, ed. N Engl J Med. 2018;378(10):931-939. doi:10.1056/NEJMcp1702514.
Primary Sjögren’s syndrome is a common systemic autoimmune disease, with a female-to-male predominance of 9:1 and peak incidence at approximately 50 years of age. The hallmark of the disease is exocrinopathy, which often results in dryness of the mouth and eyes, fatigue, and joint pain. These three symptoms are present in more than 80% of the patients with this disease and have a major effect on quality of life, primarily because of disabling fatigue, with associated loss of work productivity. This condition may occur in isolation or in association with organ-specific autoimmune diseases, such as thyroiditis or primary biliary cirrhosis or cholangitis, in which case the disease is referred to as primary Sjögren’s syndrome. In contrast, the term secondary, or associated, Sjögren’s syndrome has been used when the disease occurs in association with another systemic autoimmune disease.
The risk of B-cell lymphoma is 15-20 times as high among patients with primary Sjögren’s syndrome as in the general population (lifetime risk, 5 to 10%), a finding that has been attributed to the chronic B-cell activation in this condition. These lymphomas are mostly B-cell non-Hodgkin’s lymphomas, with a predominance of the low grade, marginal-zone histologic type. Lymphomas often develop in organs in which primary Sjögren’s syndrome is active, such as the salivary glands, and thus are primarily mucosa-associated lymphoid tissue (MALT) lymphomas. Features that are associated with an increased risk of lymphoma among patients with primary Sjögren’s syndrome can be assessed by clinical examination or by readily available blood tests.
Factors that increase risk include:
Recurrent swelling of parotid glands
Splenomegaly, lymphadenopathy, or both
Purpura
Rheumatoid factor
Cryoglobulinemia
Low C4 level
CD4 T-cell lymphocytopenia
Presence of ectopic germinal centers
The simplest of these tests (lymphocyte count, protein electrophoresis, rheumatoid factor, C3 and C4 protein, and cryoglobulin) are recommended every 1 to 2 years.
Treatment relies on muscarinic agonists (pilocarpine hydrochloride and cevimeline hydrochloride). The main adverse effect of these agents is sweating, which can be minimized by gradual escalation of the dose. In the absence of trials involving patients with primary Sjögren’s syndrome, severe organ manifestations are treated with immunosuppressive agents (including prednisone, methotrexate, mycophenolate sodium, azathioprine, and cyclophosphamide), in accordance with guidelines for systemic lupus erythematosus and other connective-tissue diseases.
Kolakshyapati M, Adhikari RB, Karlowee V, et al. Nonenhancing peritumoral hyperintense lesion on diffusion-weighted imaging in glioblastoma: a novel diagnostic and specific prognostic indicator. J Neurosurg. 2018;128(3):667-678. doi:10.3171/2016.10.JNS161694.
Preoperative MR images, including diffusion-weighted imaging (DWI) studies (b = 1000 and 4000 sec/mm2) were obtained in patients with newly diagnosed malignant tumor. Sixty-four patients with histologically confirmed glioblastoma, 32 patients with malignant lymphoma, and 46 patients with brain metastases were included. The presence of a nonenhancing peritumoral DWI high lesion (i.e., hyperintense lesion in a nonenhancing peritumoral area on DWI) was confirmed in both DWI sequences. Gray matter lesions were excluded. Lesions were termed “definite” if present within 3 cm of the hyperintense tumor border with a signal intensity ratio ≥ 30% when compared with the contralateral normal white matter in both sequences. Discriminant analysis between the histological diagnosis and the presence of Definite-nonenhancing peritumoral DWI high lesion was performed, as well as Kaplan-Meier survival analysis incorporating the existence of Definite-nonenhancing peritumoral DWI high lesion.
In 25% of glioblastoma patients, definite- nonenhancing peritumoral DWI high lesion was present, while it was conspicuously absent in patients with malignant lymphoma and metastatic brain tumors. The specificity and positive predictive value were 100%.
They conclude that the presence of definite- nonenhancing peritumoral DWI high lesion is very specific for glioblastoma and indicates poor prognosis. Definite- nonenhancing peritumoral DWI high lesion is a significant indicator of early local and distant/dissemination recurrence in patients with glioblastoma. Studying peritumoral DWI and high–b-value DWI is useful for tumor differentiation.
7 Tables, 5 Figures
Dalmau J, Graus F. Antibody-Mediated Encephalitis. N Engl J Med. 2018;378(9):840-851. doi:10.1056/NEJMra1708712.
Antibody-mediated encephalitides constitute a group of inflammatory brain diseases that are characterized by prominent neuropsychiatric symptoms and are associated with antibodies against neuronal cell-surface proteins, ion channels, or receptors. Common clinical features include a change in behavior, psychosis, seizures, memory and cognitive deficits, abnormal movements, dysautonomia, and a decreased level of consciousness. There are, however, no systemic manifestations other than autonomic dysfunction, and this group of diseases is separable from traditional autoimmune disorders such as systemic lupus erythematosus, which may affect the nervous system. Also separate from this group of antibody-mediated encephalitides are several disorders, some of which are paraneoplastic, such as cerebellar degeneration, neuromyelitis optica, and stiff-person spectrum diseases.
The estimated annual incidence of all types of encephalitis is approximately 5 to 8 cases per 100,000 persons, and in 40 to 50% of the cases, the cause cannot be established.
A prospective, multicenter, population-based study suggests that autoimmune disorders are the third most common cause of encephalitis, after infections (usually viral) and acute disseminated encephalomyelitis, which is typically a postinfectious disorder. A study from a center that is specifically concerned with the epidemiology of encephalitis showed that the frequency of the most common form of autoimmune encephalitis, the type with antibodies against the N-methyl-d aspartate receptor (NMDAR), surpassed the frequency of any individual viral cause of encephalitis in young persons.
Beginning in the 1980s, studies of paraneoplastic neurologic syndromes associated with antibodies against intracellular neuronal antigens informed subsequent clinical and laboratory research on the autoimmune encephalitides. The distinction between these two groups of disorders is important because some of the triggers and syndromes are similar but their pathogenic mechanisms and outcomes are different. In the autoimmune encephalitides, the antibodies bind to extracellular epitopes of cell-surface proteins and cause reversible neuronal dysfunction. These features may explain the better outcomes for patients with autoimmune encephalitides, as compared with the outcomes for patients with neurologic syndromes related to antibodies against intracellular proteins, in which neuronal loss is frequent and cytotoxic T-cell mechanisms predominate.
Two potential triggers of autoimmune encephalitides are tumors and viral encephalitis. Some of the implicated tumors contain nerve tissue or the tumor cells express the neuronal proteins targeted by the autoantibodies, suggesting that the ectopic expression of these proteins may play a role in initiating the autoimmune response. Herpes simplex encephalitis, and possibly other viral encephalitides, can trigger antibodies against the NMDAR and other neuronal cell-surface proteins; such antibodies might explain relapsing neurologic symptoms that arise weeks after the onset of herpes simplex encephalitis. This delayed complication affects approximately 20% of patients with herpes simplex encephalitis.
Treatment recommendations are based largely on retrospective series and expert opinion since few clinical trials have been conducted. The current approach includes immunotherapy and removal of the immunologic trigger, such as teratoma or another tumor, when applicable.
In practice, most patients are treated with glucocorticoids, intravenous immune globulin, or plasma exchange, and if there is no clinical response, rituximab and cyclophosphamide are used.
3 Figures, 1 Table. 1 Figure of MR appearance.
