Cervical kyphotic deformity

Cervical kyphotic deformity

Cervical kyphotic deformity, its a cervical spine deformity with a loss of curve in the neck compared to the natural lordosis.

These conditions appear as a curvature of the neck and are neck deformities that cause neck pain and instability.

The stability of the cervical spine, and its ability to resist kyphosis, depends on several different parts of the spine. First, the vertebral bodies need to be strong enough to support the head and keep a normal shape. Second, the facet joints, ligaments, and soft tissues in the back of the spine must be strong enough to keep the neck from curving forward due to the pull of the weight of the head. Finally, the muscles in the back must be strong enough to resist the forward pull of the weight of the head. If there is damage to any of these three areas, a kyphotic deformity can develop. After the kyphosis begins, the weight of the head can cause a progression of the curvature.


Patients with cervical kyphotic deformity exhibit different patterns of reciprocal changes depending on whether they have head-balanced or trunk-balanced kyphosis. These reciprocal changes should be considered to in order to prevent secondary spine disorders. It is important to evaluate the global spinal alignment to assess postoperative changes 1)

Cervical kyphosis can be classified into two different groups:

type 1 flexible cervical kyphosis

type 2 fixed cervical kyphosis.

The treatment option for correcting a cervical kyphotic deformity is currently controversial. Lots of studies examined the one/stage combined anterior-posterior treatment, although the rate of fusion and the long term follow up controls are rarely mentioned in the literature 2) 3) 4) 5) 6) 7) 8).


Fusion of cervical spine in kyphosis alignment has been proven to produce an acceleration of cervical adjacent segment disease. Stand-alone cervical cages are reported to have a relatively high incidence of implant subsidence with secondary kyphotic deformity. This malalignment may theoretically lead to adjacent segment disease in the long term.

A prospective study analysed possible risk factors leading to cage subsidence with resulting sagittal malalignment of cervical spine. Radiographic data of 100 consecutive patients with compressive radiculo-/myelopathy due to degenerative disc prolapse or osteophyte formation were prospectively collected in those who were treated by anterior cervical discectomy and implantation of single type interbody fusion cage. One hundred and forty four implants were inserted altogether at one or two levels as stand-alone cervical spacers without any bone graft or graft substitute. All patients underwent standard anterior cervical discectomy and the interbody implants were placed under fluoroscopy guidance. Plain radiographs were obtained on postoperative days one and three to verify position of the implant. Clinical and radiographic follow-up data were obtained at 6 weeks, 3 and 6 months and than annually in outpatient clinic. Radiographs were evaluated with respect to existing subsidence of implants. Subsidence was defined as more than 2 mm reduction in segmental height due to implant migration into the adjacent end-plates. Groups of subsided and non-subsided implants were statistically compared with respect to spacer distance to the anterior rim of vertebral body, spacer versus end-plate surface ratio, amount of bone removed from adjacent vertebral bodies during decompression and pre- versus immediate postoperative intervertebral space height ratio. There were 18 (18%) patients with 19 (13.2%) subsided cages in total. No patients experienced any symptoms. At 2 years, there was no radiographic evidence of accelerated adjacent segment degeneration. All cases of subsidence occurred at the anterior portion of the implant: 17 cases into the inferior vertebra, 1 into the superior and 1 into both vertebral bodies. In most cases, the process of implant settling started during the perioperative period and its progression did not exceed three postoperative months. There was an 8.7 degrees average loss of segmental lordosis (measured by Cobb angle). Average distance of subsided intervertebral implants from anterior vertebral rim was found to be 2.59 mm, while that of non-subsided was only 0.82 mm (P < 0.001). Spacer versus end-plate surface ratio was significantly smaller in subsided implants (P < 0.001). Ratio of pre- and immediate postoperative height of the intervertebral space did not show significant difference between the two groups (i.e. subsided cages were not in overdistracted segments). Similarly, comparison of pre- and postoperative amount of bone mass in both adjacent vertebral bodies did not show a significant difference. Appropriate implant selection and placement appear to be the key factors influencing cage subsidence and secondary kyphotisation of box-shaped, stand-alone cages in anterior cervical discectomy and fusion. Mechanical support of the implant by cortical bone of the anterior osteophyte and maximal cage to end-plate surface ratio seem to be crucial in the prevention of postoperative loss of lordosis.

The results were not able to reflect the importance of end-plate integrity maintenance; the authors would, however, caution against mechanical end-plate damage. Intraoperative overdistraction was not shown to be a significant risk factor in this study. The significance of implant subsidence in acceleration of degenerative changes in adjacent segments remains to be evaluated during a longer follow-up 9).

There are several causes of cervical kyphosis. This condition can develop in children and adults.

The first cause is degenerative disc disease. The process of degeneration of the intervertebral discs causes many spine problems. In older adults, the wear and tear of aging on the discs between each vertebra can cause the disc to collapse. As the discs collapse and grow thinner, the head tilts forward and the neck begins to curve forward. This begins a process that may continue to progress for years. The weight of the head causes an imbalance of forces pushing the neck increasingly forward. This slowly leads to an increasing curve and may end with a kyphosis.

The second cause of cervical kyphosis is congenital, meaning it is a birth defect affecting the development of the spine. A person is born with some sort of defect, such as incomplete formation of the spine, which leads to an increasing kyphosis type curve in the neck. Congenital kyphosis usually leads to a growth disturbance of the vertebrae themselves. Instead of growing normally, the vertebrae grow into a triangular-shape with the small end pointing forward. Because the vertebrae are stacked one atop the other, the triangle shape causes the spine to have a forward curvature.

When a child has congenital kyphosis, there are generally additional birth defects in other areas of the body. Most commonly, there are defects of the kidneys and urinary system.

Treatment for congenital kyphosis is typically surgery. Early surgical intervention usually produces the best results and can prevent progression of the curve. The type of surgical procedure will depend on the nature of the abnormality. Conservative (non-surgical) treatment plans do not have much success at correcting this type of kyphosis. Without surgery, there is a critical need for observation and close medical follow-up to prevent serious problems.

The third cause of cervical kyphosis is traumatic, meaning it is the result of an injury to the cervical spine. This may be from a compression fracture of the vertebrae or from an injury to the ligaments in the back of the cervical spine. When a compression fracture of the vertebra occurs, the vertebral body may heal in a wedge shape. This causes a similar situation discussed above for the triangle-shaped vertebrae of a congenital kyphosis. The resulting imbalance can lead to increasing forward curvature of the neck. If the kyphosis becomes bad enough, it can narrow the spinal canal causing a condition known as spinal stenosis. Pressure on the spinal cord due to the narrowing can lead to neurological problems, such as pain, numbness, and a loss in muscle strength.

The fourth, and the most common cause of cervical kyphosis, is iatrogenic. Iatrogenic means the problem results from the effects of a medical treatment, such as surgery. Kyphosis following laminectomy surgery is quite common. It happens much more frequently with children than with adults.

Problems can also arise if the fusion fails to heal properly. Failure of a fusion site to heal is called a pseudoarthrosis. If the fusion fails to heal, the spine may begin to curve forward leading to a kyphosis. Even in a healed fusion, improper alignment of the fused vertebrae can result in an imbalance that leads to a kyphosis.

Other less common causes of cervical kyphosis include infection in the spine, tumors of the spine, and systemic diseases that affect the spine (such as ankylosing spondylitis). A cervical kyphosis may also occur years after radiation therapy for cancer involving the neck. The radiation therapy may affect the growth of the cervical vertebrae in children who received radiation therapy in childhood.

see Postlaminectomy kyphosis.

The symptoms of cervical kyphosis can range from a simple nuisance to a severe deformity, which can lead to paralysis if untreated. Symptoms can include mechanical neck pain if the kyphosis is due to degenerative changes in the cervical spine. You may have a reduced range of motion in the neck. This means you may not be able to rotate your neck fully and you may have difficulty looking up for any length of time.

If the kyphosis is severe, you may begin to have problems with the nerve roots or the spinal cord, due to pressure on the nerves in the cervical spine. This may cause: weakness in the arms or legs, loss of grip strength, or difficulty walking due to spasticity in the legs. You may have problems controlling your bladder or bowels. In extremely severe cases that are left untreated, paralysis from the neck down may even result.

Regular X-rays, are usually a first step in looking into any neck problem and will help determine if more tests will be needed.

Magnetic Resonance Imaging (MRI)

The MRI is the most commonly used test to evaluate the spine because it can show abnormal areas of the soft tissues around the spine. The MRI is better than X-ray because in addition to the bones, it can also show pictures of the nerves and discs. The MRI is done to find tumors, herniated discs, or other soft-tissue disorders.

Excessive kyphosis can be treated, and the methods of treatment have evolved over time. Today, surgery to treat cervical kyphosis is usually a spinal fusion combined with “segmental instrumentation”. This means that some type of metal plate or rod is used to hold the spine in the proper alignment in order to straighten it.

If the deformity is fixed (meaning that it is not getting worse), and there are no neurological problems due to pressure on the spinal cord, surgery is usually not recommended because the problem is not going to get worse. Spinal surgery is serious, and unless necessary, it is rarely recommended. However, if the fixed deformity is accompanied by neurological problems from pressure on the spinal cord, surgery becomes more likely. Surgical correction is the most difficult type of treatment for cervical kyphosis. Surgery may require an operation from the front of the spine to relieve the pressure on the spinal cord, and an operation from the back to fuse the spine and prevent the kyphosis from returning.

If the kyphosis is flexible, the decision to go ahead with surgery should be based upon: the progression of the deformity, the severity of the deformity, and the amount of pain it causes. If the curve and pain are minor, surgery will not be recommended simply because the deformity looks bad. However, if the deformity is severe and the pain is chronic, surgery may be a good option.

If the kyphosis is due to ankylosing spondylitis, the problem area of the spine usually extends over the area where the cervical and thoracic spines join each other. This type of cervical kyphosis is usually a fixed deformity. Ankylosing spondylitis (AS) causes the discs between each vertebra of the entire spine to calcify and actually creates a fusion of the entire spine. If there is a cervical kyphosis after the spine fuses due to AS, the surgery may have to include performing an “osteotomy” of the fused spine. The term osteotomy means “bone (osteo) cut (otomy)”. During an osteotomy, the front of the spine column may need to be cut to allow the surgeon to straighten the spine. The spinal cord is not cut, only the bone of the vertebrae in the front of the spinal column.


Posterior laminoplasty might be considered as a treatment option for multilevel cervical degenerative disc diseases (MCDDs) but could not be appropriate for patients with cervical kyphotic deformity 10).


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Kim CW, Hyun SJ, Kim KJ. Systematic Review of EOS Evaluations of Global Spinal Alignment : Do Not Miss the Forest for the Trees. J Korean Neurosurg Soc. 2021 Oct 8. doi: 10.3340/jkns.2020.0234. Epub ahead of print. PMID: 34619822.
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Abumi K, Shono Y, Taneichi H, Ito M, Kaneda K. Correction of cervical kyphosis using pedicle screw fixation systems. Spine (Phila Pa 1976) 1999;24:2389–2396.
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Kanter AS, Wang MY, Mummaneni PV. A treatment algorithm for the management of cervical spine fractures and deformity in patients with ankylosing spondylitis. Neurosurg Focus. 2008;24:E11.
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Ferch RD, Shad A, Cadoux-Hudson TA, Teddy PJ. Anterior correction of cervical kyphotic deformity: effects on myelopathy, neck pain, and sagittal alignment. J Neurosurg. 2004;100:13–19.
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Zdeblick TA, Bohlman HH. Cervical kyphosis and myelopathy. Treatment by anterior corpectomy and strut-grafting. J Bone Joint Surg Am. 1989;71:170–182.
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Lin D, Zhai W, Lian K, Kang L, Ding Z. Anterior versus posterior approach for four-level cervical spondylotic myelopathy. Orthopedics. 2013;36:e1431–e1436.
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Spivak J, Giordano CP. Cervical kyphosis. In: Bridwell KH, DeWald RL, eds , editors. The Textbook of Spinal Surgery. 2nd ed. Philadelphia: Lippincott-Raven; 1997. p. 1027–1038.
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Ganju A, Ondra SL, Shaffrey CI. Cervical kyphosis. Tech Orthop. 2003;17:345–354.
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Barsa P, Suchomel P. Factors affecting sagittal malalignment due to cage subsidence in standalone cage assisted anterior cervical fusion. Eur Spine J. 2007 Sep;16(9):1395-400. Epub 2007 Jan 13. PubMed PMID: 17221174; PubMed Central PMCID: PMC2200763.
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Lin JH, Chien LN, Tsai WL, Chen LY, Hsieh YC, Chiang YH. Reoperation rates of anterior cervical discectomy and fusion versus posterior laminoplasty for multilevel cervical degenerative diseases: a population-based cohort study in Taiwan. Spine J. 2016 Dec;16(12):1428-1436. doi: 10.1016/j.spinee.2016.08.017. PubMed PMID: 2752008

Resective epilepsy surgery

Resective epilepsy surgery

Resective epilepsy surgery based on an invasive EEG-monitors performed with subdural grids (SDG) or depth electrodes (stereoelectroencephalographySEEG) is considered to be the best option towards achieving seizure-free state in drug resistant epilepsy.

Despite good outcomes from high-quality clinical trials, referrals of patients with seizures refractory to medical treatment remain infrequent 1).

Three RCTs (two adult RCTs and one pediatric RCT) consistently supported the efficacy of resective surgery as treatment for epilepsy with semiology localized to the mesial temporal lobe. In these studies, 58-100% of the patients who underwent resective surgery achieved seizure freedom, in comparison to 0-13% of medically treated patients. In another RCT, the likelihood of seizure freedom after resective surgery was independent of the surgical approach (transSylvian [64%] versus subtemporal [62%]). Two other RCTs demonstrated that hippocampal resection is essential to optimize seizure control. But, no significant gain in seizure control was achieved beyond removing 2.5 cm of the hippocampus. Across RCTs, minor complications (deficit lasting < 3 months) and major complications (deficit > 3 months) ranged 2-5% and 5-11% respectively. However, nonincapacitating superior subquadrantic visual-field defects (not typically considered a minor or major complication) were noted in up to 55% of the surgical cohort. The available RCTs provide compelling support for resective surgery as a treatment for mesial temporal lobe epilepsy and offer insights toward optimal surgical strategy 2)

Complete removal of the epileptogenic zone significantly increases the chances for postoperative seizure-freedom. In complex surgical candidates, delineation of the epileptogenic zone requires a long-term invasive video/EEG from intracranial electrodes. It is especially challenging to achieve a complete resection in deep brain structures such as opercular insular cortex 3).

Belohlavkova et al. retrospectively reviewed data of pediatric patients operated in Motol Epilepsy Center between October 2010 and June 2020 who underwent resections guided by intraoperative visual detection of depth electrodes following SEEG. The outcome in terms of seizure- and AED-freedom was assessed individually in each patient.

Nineteen patients (age at surgery 2.9-18.6 years, median 13 years) were included in the study. The epileptogenic zone involved opercular insular cortex in eighteen patients. The intraoperative detection of the electrodes was successful in seventeen patients and the surgery was regarded complete in sixteen. Thirteen patients were seizure-free at final follow-up including six drug-free cases. The successful intraoperative detection of the electrodes was associated with favorable outcome in terms of achieving complete resection and seizure-freedom in most cases. On the contrary, the patients in whom the procedure failed had poor postsurgical outcome.

The reported technique helps to achieve the complete resection in challenging patients with the epileptogenic zone in deep brain structures 4)


81 patients with tuberous sclerosis complex (TSC) who had undergone resective epilepsy surgery at Sanbo Brain Hospital, between April 2004 and June 2019. They estimated the cumulative probability of remaining seizure-free and plotted survival curves. Variables were compared using Mann-Whitney U, Pearson’s correlation, continuity correction, and Fisher’s exact chi-square tests. Prognostic predictors were analyzed using log-rank (Mantel-Cox) tests and Cox regression models.

At the last follow-up, 48 (59.3%) patients were classified as International League Against Epilepsy Class 1 (including 14 patients who had seizures <3 times postoperatively on the same or different day and were seizure-free at all other times). The estimated cumulative probability of remaining seizure-free postoperatively was 69.0% (95% confidence interval [CI] 58.8-79.2%), 61.9% (95% CI 51.1-72.7%), and 55.0% (95% CI 42.8-67.2%) at 2, 5, and 10 years, respectively. The mean time of remaining seizure-free was 7.24 ± 0.634 years (95% CI 6.00-8.49); en bloc resection was an essential positive predictor of postoperative seizure freedom, as was age at seizure onset, regional interictal video-electroencephalography pattern, and temporal lobe surgery. The longer the seizure-free time, the less likely a relapse. Patients who postoperatively experienced seizures remained likely to recover.

They demonstrated the efficacy of tuberous sclerosis complex treatment and intractable epilepsy with surgery. Detailed perioperative tests are a reliable predictor of postoperative seizure freedom 5)


1)

Jobst BC, Cascino GD. Resective epilepsy surgery for drug-resistant focal epilepsy: a review. JAMA. 2015 Jan 20;313(3):285-93. doi: 10.1001/jama.2014.17426. PMID: 25602999.
2)

Cramer SW, McGovern RA, Wang SG, Chen CC, Park MC. Resective epilepsy surgery: assessment of randomized controlled trials. Neurosurg Rev. 2021 Aug;44(4):2059-2067. doi: 10.1007/s10143-020-01432-x. Epub 2020 Nov 9. PMID: 33169227.
3) , 4)

Belohlavkova A, Jahodova A, Kudr M, Benova B, Ebel M, Liby P, Taborsky J, Jezdik P, Janca R, Kyncl M, Tichy M, Krsek P. May intraoperative detection of stereotactically inserted intracerebral electrodes increase precision of resective epilepsy surgery? Eur J Paediatr Neurol. 2021 Sep 25;35:49-55. doi: 10.1016/j.ejpn.2021.09.012. Epub ahead of print. PMID: 34610561.
5)

Huang Q, Zhou J, Wang X, Li T, Wang M, Wang J, Teng P, Qi X, Zhu M, Luan G, Zhai F. Predictors and Long-term Outcome of Resective Epilepsy Surgery in Patients with Tuberous Sclerosis Complex: A Single-centre Retrospective Cohort Study. Seizure. 2021 Mar 25;88:45-52. doi: 10.1016/j.seizure.2021.03.022. Epub ahead of print. PMID:

Endoscopic transsphenoidal approach

Endoscopic transsphenoidal approach

The endoscopic transsphenoidal approach shown to be as effective as, if not more than, the traditional transseptal microscopic transsphenoidal surgery 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11).


Endoscopic transsphenoidal surgery is associated with higher gross tumor removal and lower incidence of septal perforation in patients with pituitary adenoma. Future large-scale prospective randomized controlled trials are needed to verify these findings 12)


The interest in endoscopic endonasal transsphenoidal surgery for the treatment of sellar and perisellar lesions is growing as a consequence of the results achieved in the past years and of the interest by patients, endocrinologists, and neurosurgeons. Furthermore, the special ability of the endoscope to offer a wider and detailed view of anatomic structures is a major advantage that increases the attention of neurosurgeons who seek less invasive procedures and better results. Most neurosurgeons performing transsphenoidal surgery, however, are not used to endoscopy, and changing from microsurgical to endoscopic technique can be difficult and even discouraging, often because of difficulties in the initial phase of the procedure.

With the purpose of helping minimize some of the difficulties, Cavallo et al., described useful tips and tricks that mainly concern familiarization with the endoscopic equipment, details of the transsphenoidal anatomy, and endoscopic skills. They stressed the steps and details that they judge most important.

They believed that by following these recommendations neurosurgeons can overcome, or even avoid, the difficulties frequently encountered transsphenoidal surgery, allowing them to safely and efficiently perform endonasal transsphenoidal endoscopic procedures 13).

Castle-Kirszbaum et al. described the skeletal, vascular and neural anatomical variations that could be encountered from the nasal phase, through the sphenoid phase, to the sellar phase of the operative exposure. A preoperative checklist is also provided 14)

see Transsphenoidal approach complications

A study assessed the long-term impact of endoscopic skull base surgery on olfaction, sinonasal symptoms, mucociliary clearance time (MCT), and quality of life (QoL). Patients with pituitary adenomas underwent TTEA (n = 38), while patients with other benign parasellar tumours who underwent an EEA with vascularised septal flap reconstruction (n = 17) were enrolled in this prospective study between 2009 and 2012. Sinonasal symptoms (Visual Analogue Scale), subjective olfactometry (Barcelona Smell Test-24, BAST-24), MCT (saccharin test), and QoL (short form SF-36, rhinosinusitis outcome measure/RSOM) were evaluated before, and 12 months after, surgery. At baseline, sinonasal symptoms, MCT, BAST-24, and QoL were similar between groups. Twelve months after surgery, both TTEA and EEA groups experienced smell impairment compared to baseline. Moreover, EEA (but not TTEA) patients reported increased posterior nasal discharge and longer MCTs compared to baseline. No significant changes in olfactometry or QoL were detected in either group 12 months after surgery. Over the long-term, expanded skull base surgery, using EEA, produced more sinonasal symptoms (including loss of smell) and longer MCTs than pituitary surgery (TTEA). EEA showed no long-term impact on smell test or QoL 15).

Endoscopic transsphenoidal approach case series.

Endoscopic transsphenoidal approach Instruments.

All endoscopic transphenoidal pituitary surgeries performed from January 1, 2015, to October 24, 2017, with complete data were evaluated in a retrospective single-institution study. The electronic medical record was reviewed for patient factors, tumor characteristics, and cost variables during each hospital stay. Multivariate linear regression was performed using Stata software.

The analysis included 190 patients and average length of stay was 4.71 days. Average total in-hospital cost was $28,624 (95% confidence interval $25,094-$32,155) with average total direct cost of $19,444 ($17,136-$21,752) and total indirect cost of $9181 ($7592-$10,409). On multivariate regression, post-operative cerebrospinal fluid (CSF) leak was associated with a significant increase in all cost variables, including a total cost increase of $40,981 ($15,474-$66,489, P = .002). Current smoking status was associated with an increased total cost of $20,189 ($6,638-$33,740, P = .004). Self-reported Caucasian ethnicity was associated with a significant decrease in total cost of $6646 (-$12,760 to -$532, P = .033). Post-operative DI was associated with increased costs across all variables that were not statistically significant.

Post-operative CSF leak, current smoking status, and non-Caucasian ethnicity were associated with significantly increased costs. Understanding of cost drivers of endoscopic transphenoidal pituitary surgery is critical for future cost control and value creation initiatives 16).


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Endoscopic versus microscopic trans-sphenoidal pituitary surgery: a systematic review and meta-analysis. Goudakos JK, Markou KD, Georgalas C. Clin Otolaryngol. 2011;36:212–220.
5)

Meta-analysis of endoscopic versus sublabial pituitary surgery. DeKlotz TR, Chia SH, Lu W, Makambi KH, Aulisi E, Deeb Z. Laryngoscope. 2012;122:511–518.
6)

Evaluation of trans-sphenoidal surgery in pituitary GH-secreting micro- and macroadenomas: a comparison between microsurgical and endoscopic approach. Lenzi J, Lapadula G, D’Amico T, et al. https://www.minervamedica.it/en/journals/neurosurgical-sciences/article.php?cod=R38Y2015N01A0011. J Neurosurg Sci. 2015;59:11–18.
7)

Endoscopic versus microscopic transsphenoidal surgery in the treatment of pituitary tumors: systematic review and meta-analysis of randomized and non-randomized controlled trials. Bastos RV, Silva CM, Tagliarini JV, Zanini MA, Romero FR, Boguszewski CL, Nunes VD. Arch Endocrinol Metab. 2016;60:411–419.
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Endoscopic versus microscopic approach in pituitary surgery. Gao Y, Zheng H, Xu S, Zheng Y, Wang Y, Jiang J, Zhong C. J Craniofac Surg. 2016;27:157–159.
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Resection of pituitary tumors: endoscopic versus microscopic. Singh H, Essayed WI, Cohen-Gadol A, Zada G, Schwartz TH. J Neurooncol. 2016;130:309–317.
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Endoscopic endonasal versus microsurgical transsphenoidal approach for growth hormone-secreting pituitary adenomas-systematic review and meta-analysis. Phan K, Xu J, Reddy R, Kalakoti P, Nanda A, Fairhall J. http://www.sciencedirect.com/science/article/pii/S1878875016310178. World Neurosurg. 2017;97:398–406.
11) , 12)

Endoscopic versus microscopic transsphenoidal surgery in the treatment of pituitary adenoma: A Systematic review and meta-analysis. Li A, Liu W, Cao P, Zheng Y, Bu Z, Zhou T. http://www.sciencedirect.com/science/article/pii/S1878875017300323. World Neurosurg. 2017;101:236–246.
13)

Cavallo LM, Dal Fabbro M, Jalalod’din H, Messina A, Esposito I, Esposito F, de Divitiis E, Cappabianca P. Endoscopic endonasal transsphenoidal surgery. Before scrubbing in: tips and tricks. Surg Neurol. 2007 Apr;67(4):342-7. Review. PubMed PMID: 17350397.
14)

Castle-Kirszbaum M, Uren B, Goldschlager T. Anatomical Variation for the Endoscopic Endonasal Transsphenoidal Approach. World Neurosurg. 2021 Oct 2:S1878-8750(21)01456-X. doi: 10.1016/j.wneu.2021.09.103. Epub ahead of print. PMID: 34610448.
15)

Rioja E, Bernal-Sprekelsen M, Enriquez K, Enseñat J, Valero R, de Notaris M, Mullol J, Alobid I. Long-term outcomes of endoscopic endonasal approach for skull base surgery: a prospective study. Eur Arch Otorhinolaryngol. 2015 Dec 19. [Epub ahead of print] PubMed PMID: 26688432.
16)

Parasher AK, Lerner DK, Glicksman JT, et al. Drivers of In-Hospital Costs Following Endoscopic Transphenoidal Pituitary Surgery [published online ahead of print, 2020 Aug 24]. Laryngoscope. 2020;10.1002/lary.29041. doi:10.1002/lary.29041
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