Physiology of cerebrospinal fluid circulation Purpose of review This article describes the physiology of cerebrospinal fluid (CSF). We review current evidence and new concepts relating to CSF physiology with respect to CSF secretion, circulation and resorption and we highlight key pathophysiological associations including the relationship between CSF and intracranial pressure. Recent findings CSF secretion occurs primarily via the choroid plexus. Various transport mechanisms facilitate CSF secretion but the role Aquaporins play in this process is a recent discovery and an area of ongoing research. CSF circulation is a dynamic process but the importance of the perivascular ‘Glymphatic system’ and extraarachnoidal pathways of resorption are relatively new concepts. Summary CSF physiology is dependent on various interacting factors and is critical for normal brain development and function. Correspondence to Jonathan Shapey, Wellcome/EPSRC Centre for Interventional and Surgical Sciences (WEISS), Charles Bell House, 1st Floor, 43-45 Foley Street, London W1W 7TS, United Kingdom. E-mail: j.shapey@ucl.ac.uk Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

Cerebrospinal fluid physiology No abstract available

Optimizing value in head and neck cancer free flap surgery Purpose of review Value has become an increasingly important topic in healthcare delivery as our systems attempt to deliver increased value to patients at lower costs. This review highlights research performed regarding value for head and neck cancer reconstruction in three evolving areas: care pathway development, virtual surgical planning (VSP), and free flap versus locoregional flap reconstruction. Recent findings Improvements in quality-driven patient care in head and neck free tissue transfer are possible in a number of areas. Care pathways and appropriate management of patients prone to comorbidities decrease hospital length of stay and readmission rates. Further, high-cost hospital stays partially driven by ICU admissions may be reduced by step-down units. Intraoperatively, VSP may reduce operative time in difficult cases and careful selection of free versus locoregional flap reconstruction may decrease cost, operative time, and complications after surgery. Summary Head and neck reconstruction is a costly endeavor both for the patient and the healthcare system. Careful consideration of practices which may improve outcomes for patients while maximizing efficiency is necessary in our changing healthcare landscape, and providers should identify areas for improvement in their own practices. Further study within the field of head and neck oncology that are specific and data-driven are necessary. Correspondence to Jeffrey J. Houlton, Department of Otolaryngology – Head and Neck Surgery, University of Washington Medical Center, 1959 NE Pacific St., Box 356515, Seattle, WA 98195, USA. E-mail: jhoulton@uw.edu Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

Reconstruction of animal bite injuries to the head and neck Purpose of review The aim if this review is to provide an update on the existing literature of animal bite treatment strategies and provide a systematic approach to animal bites from presentation to reconstruction. Recent findings Dog bites cause 80–90% of animal bites with 26.8–56.5% occurring in the head and neck. Infection rates may be as low as 5.7–9.7%. Primary closure alone is sufficient in 69.8% of dog bites within the first 24 h. Summary Animal bite injuries to the head and neck are common, especially in the younger population. Dogs cause a majority of these bite injuries. Injuries can include simple lacerations or punctures, avulsions with tissue present, or avulsions with loss of tissue. The most common locations are the cheek, nose, and lips. It is important to gather the vaccination status of the animal and patient and to administer tetanus/rabies prophylaxis if indicated. Antibiotics are typically prescribed for 3–5 and 7–14 days for uninfected and infected wounds, respectively. These wounds require evaluation, irrigation, and occasionally debridement or repair in the operating room. The type of repair is determined based on the location and extent of injury and can range from primary closure to microsurgical replantation, skin grafts, flaps, or even facial transplantation. Correspondence to John J. Chi, MD, MPHS, Department of Otolaryngology – Head and Neck Surgery, Division of Facial Plastic & Reconstructive Surgery, Washington University School of Medicine, 660 S. Euclid Avenue, Campus Box 8115, St. Louis, MO 63110, USA. Tel: +1 314 996 3881; e-mail: JChi@wustl.edu Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

Reconstruction of the mandible for osteoradionecrosis Purpose of review To describe current standard of care for osteoradionecrosis (ORN) of the mandible and report possible future trends. Recent findings Cutting guides may be used to reduce surgical time and possibly improve outcomes. There has also been recent investigation into the use of pentoxifylline and tocopherol or pentoxifylline, tocopherol and clodronate (a well known conservative medial regime) as a prevention for development of ORN after dental extractions and the first randomized controlled study is upcoming. Augmented reality has shown promise as a comparable and inexpensive possible alternative to cutting guides. Summary Current standard of care involves conservative/supportive therapy with antioxidants, antibiotics, steroids, and pain control for low-grade ORN with surgery reserved for high-grade/progressive ORN with refractory to conservative therapy and with significant oral dysfunction. Correspondence to Orly M. Coblens, MD, Assistant Professor, Department of Otolaryngology – Head and Neck Surgery, University of Texas Medical Branch, Galveston, Texas, USA. Tel: +1 409 772 2701; e-mail: orcoblen@utmb.edu Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

Use of multiple free flaps in head and neck reconstruction Purpose of review To review the recent literature on the use of multiple flaps in head and neck reconstruction with attention to form, function, outcomes, and complications. Recent findings Multiple free flap reconstructions are technically feasible with high flap survival rates, tolerable complication rates, and overall adequate functional and aesthetic outcomes, given the large extent of the defects and the high surgical complexity of these cases. Summary Multiple free flap reconstructions should be considered in cases of large defects involving multiple functional regions and tissue types, which most often arises following resection of advanced malignancies. As there is mortality benefit with clear surgical margins and eradication of malignant lymph nodes, larger resections should be pursued if necessary, followed by a multiple flap reconstruction. Correspondence to Arnaud Bewley, MD, Department of Otolaryngology-Head and Neck Surgery, UC Davis Medical Center, 2521 Stockton Blvd., Suite 7200, Sacramento, CA 95817, USA. E-mail: abewley@ucdavis.edu Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

Postoperative management of patients with spontaneous cerebrospinal fluid leak Purpose of review To explore key management principles and outcomes following surgical intervention for spontaneous CSF leaks of the lateral skull base. Recent findings Outcomes following surgery for spontaneous CSF leaks of the lateral skull base depend on the surgical approach utilized. The approach reported most frequently in the literature is currently the middle fossa approach. Mean leak recurrence rates, regardless of approach, were approximately 6%. The lowest leak recurrence rates were associated with the combined middle cranial fossa-transmastoid approach. A multilayer closure was employed in all of the reviewed investigations, but the choice of reconstructive material did not significantly affect outcomes. Direct surgical complications rates, overall, were low at less than 2%. Meningitis, intracranial hemorrhage, and perioperative seizure activity were only rarely encountered. A concomitant diagnosis of idiopathic intracranial hypertension was found to be associated with increased rates of leak recurrence and sequential leak development at other skull base sites. Summary Postoperative management of patients with spontaneous CSF leaks of the lateral skull base has unique challenges. Observation of key treatment principles can lead to good outcomes and limit morbidity. A high index of suspicion should exist for concomitant idiopathic intracranial hypertension. Correspondence to Shawn M. Stevens, MD, Barrow Neurological Institute, 2222 E Highland Avenue, Ste 204, Phoenix, AZ 85016, USA. Tel: +1 602 264 4834; e-mail: sstevens@aocphysicians.com Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

Diagnosis and management of spontaneous cerebrospinal fluid fistula and encephaloceles Purpose of review To describe the current state in the diagnosis and management of spontaneous cerebrospinal fluid (sCSF) fistula and encephaloceles. Recent findings The increased incidence of obesity has resulted in more cases of sCSF fistula and encephaloceles. Obesity results in increased intracranial pressure and a greater chance of developing a sCSF fistula or encephalocele. Obstructive sleep apnea can also result in transient increase in intracranial pressure and has been shown to be common in patients with sCSF fistula. Treatment of CSF fistula is usually necessary because of the increased risk of meningitis. The use of hydroxyapatite bone cements to repair the temporal bone defects has been described with a high success rate of closing the fistula and a low complication rate. Concurrent superior semicircular canal dehiscent can be seen in up to 15% of cases and should be suspected during the surgical approach to avoid potential sensorineural hearing loss and chronic imbalance. Summary sCSF fistula and encephaloceles are an uncommon cause of hearing loss, middle ear effusion, and otorrhea, but should be recognized and repaired because of the risk of meningitis. Correspondence to Joe Walter Kutz Jr., MD, Associate Professor, Department of Otolaryngology, University of Texas Southwestern Medical Center, 2100 Inwood Dr., Dallas, TX 75390, USA. Tel: +1 214 648 3102; fax: +1 214 648 9122; e-mail: walter.kutz@utsouthwestern.edu Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

Trans-mastoid approach for cerebrospinal fluid leak repair Purpose of review To describe the technique and discuss the advantages and outcomes of the trans-mastoid approach (TMA) for temporal bone cerebrospinal fluid (CSF) leak. Recent findings TMA for CSF leak repair is an alternative to middle cranial fossa approach (MCFA) with less morbidity and good outcomes. Summary Persistent CSF leak in the temporal bone whether idiopathic, congenital or acquired, is an indication for surgery. TMA is a valid option for surgery, competing with MCFA in selected cases. Surgical technique consists of a standard mastoidectomy, exposure of the osteodural defect, and repairing it using multiple layers in an inlay and overlay fashion. Outcomes show low recurrence and complication rates with good hearing results. However, long-term follow-up should be made, as recurrences can be delayed. Correspondence to Alexandre Karkas, MD, PhD, Service ORL, Hopital Nord, Batiment B. 42055, Saint-Etienne, Cedex 2, France. Tel: +33 4 77 82 80 00; e-mail: Alexandre.Karkas@chu-st-etienne.fr Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

Update on treatment options for blast-induced hearing loss Purpose of review The incidence of blast injuries has increased, and the ear is the highest risk organ. Ear injury induced by blast exposure is important in both military and civilian conditions. The permanent hearing loss caused by blast exposure is associated with a decline in the quality of life. In this review, I describe recent therapeutic strategies for each of the ear pathologies caused by blast exposure. Recent findings For tympanic membrane perforation after blast exposure, basic fibroblast growth factor (bFGF) has been used as a less invasive treatment to repair the tympanic membrane. The closure rates of tympanic membrane perforations treated with bFGF were reported to be comparable to those following conventional tympanoplasty. For sensorineural hearing loss after blast exposure, treatment with neurotrophic factors, such as nerve growth factor (NGF) or neurotrophin-3, antioxidants, and Atoh1 induction have recently been applied, and some of them were considered for clinical application. Summary Recent advances of therapeutics for blast-induced hearing loss, based on their pathologies, have been outlined. There are several promising therapeutic approaches for both middle and inner ear disorders after blast exposure; however, further research is needed to establish new treatments for blast-induced hearing dysfunction. Correspondence to Kunio Mizutari, MD, PhD, Department of Otolaryngology, Head and Neck Surgery, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan. Tel: +81 4 2995 1511; fax: +81 4 2996 5212; e-mail: tari@mbf.ocn.ne.jp Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.