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Waste clearance (WC) is an essential process for brain homeostasis, which is required for the proper and healthy functioning of all cerebrovascular and parenchymal brain cells. This review features our current understanding of brain WC, both within and external to the brain parenchyma. We describe the interplay of the blood-brain barrier (BBB), interstitial fluid (ISF), and perivascular spaces within the brain parenchyma for brain WC directly into the blood and/or cerebrospinal fluid (CSF). We also discuss the relevant role of the CSF and its exit routes in mediating WC. Recent discoveries of the glymphatic system and meningeal lymphatic vessels, and their relevance to brain WC are highlighted. Controversies related to brain WC research and potential future directions are presented.

One of the most challenging aspects of treating disorders of the central nervous system (CNS) is the efficient delivery of drugs to their targets within the brain. Only a small fraction of drugs is able to cross the blood–brain barrier (BBB) under physiological conditions, and this observation has prompted investigation into the routes of administration that may potentially bypass the BBB and deliver drugs directly to the CNS. One such route is the intranasal (IN) route. Increasing evidence has suggested that intranasally-administered drugs are able to bypass the BBB and access the brain through anatomical pathways connecting the nasal cavity to the CNS. Though the exact mechanisms regulating the delivery of therapeutics following IN administration are not fully understood, current evidence suggests that the perineural and perivascular spaces of the olfactory and trigeminal nerves are involved in brain delivery and cerebral perivascular spaces are involved in widespread brain distribution. Here, we review evidence for these delivery and distribution pathways, and we address questions that should be resolved in order to optimize the IN route of administration as a viable strategy to treat CNS disease states.

Although tibial nerve modulation has shown to induce positive changes in the overactive bladder (OAB), prolonged therapeutic effects using percutaneous stimulation have not yet been achieved. Intradetrusor onabotulinum toxin A injection can provide prolonged therapeutic effects; however, its delivery requires invasive measures. By applying local relief of tibial nerve neural entrapment with onabotulinum toxin A injection, this study investigated the feasibility and efficacy of combining the abovementioned two therapeutic strategies. An OAB animal model was developed using 12 adult Sprague-Dawley rats with cyclophosphamide intraperitoneal injection. A perineural injection site comparable to the tibial nerve perineural injection site and corresponding to that in humans was identified and developed in rats. The toxin was injected five days after establishing the OAB. The incision was made in the skin on the lateral surface of the thigh. The biceps femoris muscle was cut across, exposing the sciatic nerve and its three terminal branches: the sural, common peroneal, and tibial nerves, and 100 units of onabotulinum toxin A was injected into the surrounding tissue. Five days following injection, cystometry was performed. Inter-contraction time, contraction pressure, and interval of the disease state improved with statistical significance. The OAB animal model showed significant improvement with the tibial nerve perineural injection of botulinum toxin, thereby suggesting the possibility of a comparable treatment adaptation in humans.

Perineural space invasion (PSI) represents a poor prognostic factor in various carcinomas. Studies on PSI in cervical cancer patients are scarce and report discrepant results regarding its incidence and prognostic value. The aim of the following study was to evaluate the occurrence rate and prognostic significance of parametrial PSI in patients cervical cancer (FIGO IB1-IIB), accompanied by high-risk factors for recurrence. We reviewed clinical records and pathology slides of patients with cervical cancer after radical hysterectomy. Only patients with at least one of following factors: Depth of invasion of ≥15 mm, parametrial and lymph node involvement, were enrolled in the study. A total of 50 patients fulfilled the above mentioned criteria. Parametrial PSI was found in 9 (18%) patients (Group I), whereas the remaining 41 (82%) subjects constituted group II. The presence of PSI proved to correlate with the depth of invasion of ≥15 mm (P=0.006) and tumor size of ≥40 mm (P=0.01), as well as a more advanced stage of the disease (P=0.04). No statistically significant differences in recurrence-free survival rate between the two groups were observed. We were able to correlate parametrial PSI with the depth of invasion, tumor size and more advanced stage of the disease in early-stage cervical cancer with high-risk of recurrence. No association with a worse prognosis was observed.

A 53-year-old man presented with a 5-month history of visual loss in his left eye. Visual acuity could be corrected to 20/20 with an increased hyperopic correction. Dilated funduscopy showed faint choroidal folds and elevation of the left optic disc. The coronal view of T2-weighted magnetic resonance imaging demonstrated a fluid-filled dilated sheath surrounding normal optic nerves. General physical examination and cerebrospinal fluid analysis were normal. The subject was diagnosed as having dural ectasia of the optic nerve sheath and followed a course of acetazolamide 250 mg twice daily for three months, and displayed good anatomical and functional results during a 2-year follow-up period. Despite the fact that several authors have recommended an optic nerve decompression, most of the patients follow a benign clinical course. The role of corticosteroids is not described in the literature. Raised levels of proteins in the cerebrospinal fluid in the perioptic subarachnoidal space could be a determining factor. On the basis of an osmotic gradient between the cerebral subarachnoid space and perioptic subarachnoid space, carbonic anhydrase inhibitors could be beneficial. In contrast to other reports, we believe that surgical intervention could be reserved for patients with rapid or progressive optic nerve dysfunction.

The differential diagnosis of a masticator space (MS) lesion is broad, owing in part to the multiple structures contained within such a small region. It is also because the MS is adjacent to many of the other deep spaces within the head and neck, which can act as gateways for disease spread. Therefore, emergency radiologists must be familiar with anatomy of the MS, as well as adjacent spaces in order to provide an accurate diagnosis to the referring clinician. This article illustrates the anatomy and common pathologies within the MS using a case-based multimodality approach. Common masticator space pathologies can be categorized into inflammatory/infectious, neoplastic, and vasoformative lesions. Important imaging features of MS lesions and patterns of disease spread will be discussed, with the aim of making this complex deep space more approachable in the emergent setting.

Introduction Symptomatic perineural cysts are rare. Resection and closure of such cysts sometimes results in postoperative neurological deficits and they can recur. We report two cases of symptomatic perineural cysts treated with subarachnoid shunts. Materials and Methods Case 1: A 62-year-old woman presented with bladder dysfunction. We identified a cyst communicating with the subarachnoid space adjacent to the S2 nerve root and implanted a subarachnoid shunt. Seven years after this surgery, her bladder dysfunction had not recurred. Case 2: A 35-year-old woman had low back pain, radiculopathy and bladder dysfunction. We identified a cyst adjacent to the S1 nerve root and implanted a subarachnoid shunt. Her low back pain and radiculopathy improved immediately and she experienced neither postoperative neurological deficits nor recurrence. Conclusion Cyst–subarachnoid shunts are a useful treatment option for symptomatic perineural cysts.

BackgroundLumbar microdiscectomy is a common procedure with satisfactory results; however, postoperative events like progressive adjacent level degeneration and perineural fibrosis can contribute to long-term pain. The purpose of the study was to evaluate MRI changes 5 years after lumbar microdiscectomy and assess their association with clinical parameters.Materials and methodsA prospective study enrolling 61 patients who underwent microdiscectomy. Changes between preoperative and postoperative MRI findings were recorded, and these findings were tested for associations with demographic, clinical and perioperative parameters. The measured imaging parameters were degeneration of the operated and adjacent discs and endplates, morphology of the disc herniation, facet joints arthritis and the presence of postoperative perineural fibrosis.ResultsStatistically significant differences were found between preoperative and postoperative morphology of the operated disc, facet joints arthritis and degeneration of the operated and caudal adjacent disc. There were no differences between preoperative and postoperative disc degeneration of the superior adjacent disc and in degeneration of the operated and adjacent endplates. Postoperatively perineural fibrosis was common; however, thecal sac compression and nerve root impingement were reduced. Age at the time of surgery was the only parameter associated with postoperative changes.ConclusionFive years after microdiscectomy, several postoperative MRI changes including operated disc’s morphology, facet joints arthritis and degeneration of the operated and caudal adjacent disc were shown. Taking into consideration that participants were on average middle-aged, these changes could be attributed not only to the impact of the surgery but also to the natural history of lumbar spine degeneration.

Herniated intervertebral disc causes in a great number of cases of lumbar nerve root compression, especially in the segment L5/S1. Other reasons responsible for stress to the lumbar spinal root are the spinal canal stenosis and the postdiscotomy syndrome. For patients without neurological deficiencies, the conservative treatment includes different epidural injection techniques. Steroids are often applied. A specific injection technique needing only a small drug amount is the epidural perineural approach using a special two-needle technique. The anatomical spaces of the nerve roots have received little attention in therapy. We have determined the anterolateral epidural space nerve volume of the nerve root L5/S1, and compared the data collected in an anatomical study with operative measurements during discectomy. The volume determination in the human cadavers was performed with liquid silicone filling the anterolateral space after dissection. The in vivo measurements were performed during surgery at the site of the anterolateral space after discectomy. The anatomical studies showed us a mean value volume of 1.1 ml. The surgical volume determinations result in a mean volume of 0.9 ml. A better understanding of the anterolateral epidural space may allow a reduction of the injection volume in the conservative nerve root compression treatment, especially using the epidural perineural technique, avoiding the risk of side effects of high doses of steroids.

Purpose To analyze, from 1.5 Tesla (T) MRI clinical cases, anatomical accessibility of nasopharyngeal tumors through the pharyngobasilar fascia (PBF) to the mandibular nerve for potential perineural spread. Methods A 6-year retrospective review of 1.5 T MR images were rated for tumor involvement of fascial planes and perineural spread in 15 consecutive patients (10 female, 5 male; mean age 45.8 years, range 19–86) with histopathologically proven tumors of the nasopharynx and referrals for radiotherapy due to intracranial extension. Results Nasopharyngeal tumors were best appreciated on T1 fat-saturated, post-gadolinium MRI. Tumors extended through the sinus of Morgagni in all cases. This sinus is a defect in the PBF through which the Eustachian tube and levator veli palatini muscle gain access to the nasopharynx. In six patients, the PBF and tensor veli palatini fascia were breached anteriorly with tumor infiltration of the tensor veli palatini and medial pterygoid muscles. In 13 cases, tumor breached the posterolateral PBF with extension into the poststyloid parapharyngeal space. In three subjects, 3 T images were also acquired and exhibited superior delineation of the anatomy and perineural tumor spread. Conclusions At 1.5 T, images showed nasopharyngeal tumors extending through the PBF into the masticator and parapharyngeal spaces, with access to the mandibular nerve and potential for perineural spread. At 3 T, soft tissue resolution appeared superior to 1.5 T. This may reflect not only the increased field strength, but an improved technique and matrix, and future studies are necessary to confirm this observation. Awareness of this anatomy for radiation and surgical planning is essential and may improve the ability for obtaining negative margins, and increasing overall survival.