Sweet spot

Sweet spot

The sweet spot is a place where a combination of factors results in a maximum response for a given amount of effort.

The results of a study of Zolal et al. suggested the possibility that atlas-based clustering, as well as diffusion tractography-based parcellation, can be useful in estimating the stimulation target (“sweet spot”) for Subthalamic deep brain stimulation for Parkinson’s disease. Atlas-based as well as diffusion-based clustering might become a useful tool in DBS trajectory planning 1).


Stimulation effects of 449 DBS settings in 21 PD patients were clinically and quantitatively assessed through standardized monopolar reviews and mapped into standard space. A sweet spot for best motor outcome was determined using voxelwise and nonparametric permutation statistics. Two independent cohorts were used to investigate whether stimulation overlap with the sweet spot could predict acute motor outcome (10 patients, 163 settings) and long-term overall Unified Parkinson’s Disease Rating Scale Part III (UPDRS-III) improvement (63 patients).

Results: Significant clusters for suppression of rigidity and akinesia, as well as for overall motor improvement, resided around the dorsolateral border of the STN. Overlap of the volume of tissue activated with the sweet spot for overall motor improvement explained R2 = 37% of the variance in acute motor improvement, more than triple what was explained by overlap with the STN (R2 = 9%) and its sensorimotor subpart (R2 = 10%). In the second independent cohort, sweet spot overlap explained R2 = 20% of the variance in long-term UPDRS-III improvement, which was equivalent to the variance explained by overlap with the STN (R2 = 21%) and sensorimotor STN (R2 = 19%).

Interpretation: This study is the first to predict clinical improvement of parkinsonian motor symptoms across cohorts based on local DBS effects only. The new approach revealed a distinct sweet spot for STN DBS in PD. Stimulation overlap with the sweet spot can predict short- and long-term motor outcome and may be used to guide DBS programming 2).


Based on local field potential data acquired from 54 patients undergoing STN-DBS, power values within alpha, beta, low beta, and high beta bands were calculated. Values were projected into common stereotactic space after DBS lead localization. Recorded beta power values were significantly higher at posterior and dorsal lead positions, as well as in active compared with inactive pairs. The peak of activity in the beta band was situated within the sensorimotor functional zone of the nucleus. In contrast, higher alpha activity was found in a more ventromedial region, potentially corresponding to associative or premotor functional zones of the STN. Beta- and alpha-power peaks were then used as seeds in a fiber tracking experiment. Here, the beta-site received more input from primary motor cortex whereas the alpha-site was more strongly connected to premotor and prefrontal areas. The results summarize predominant spatial locations of frequency signatures recorded in STN-DBS patients in a probabilistic fashion. The site of predominant beta-activity may serve as an electrophysiologically determined target for optimal outcome in STN-DBS for PD in the future 3).

References

1)

Zolal A, Polanski WH, Klingelhoefer L, Kitzler HH, Linn J, Podlesek D, Sitoci-Ficici KH, Reichmann H, Leonhardt GK, Schackert G, Sobottka SB. Parcellation of the Subthalamic Nucleus in Parkinson’s Disease: A Retrospective Analysis of Atlas- and Diffusion-Based Methods. Stereotact Funct Neurosurg. 2020 Sep 23:1-8. doi: 10.1159/000509780. Epub ahead of print. PMID: 32966999.
2)

Dembek TA, Roediger J, Horn A, Reker P, Oehrn C, Dafsari HS, Li N, Kühn AA, Fink GR, Visser-Vandewalle V, Barbe MT, Timmermann L. Probabilistic sweet spots predict motor outcome for deep brain stimulation in Parkinson disease. Ann Neurol. 2019 Oct;86(4):527-538. doi: 10.1002/ana.25567. PMID: 31376171.
3)

Horn A, Neumann WJ, Degen K, Schneider GH, Kühn AA. Toward an electrophysiological “sweet spot” for deep brain stimulation in the subthalamic nucleus. Hum Brain Mapp. 2017 Jul;38(7):3377-3390. doi: 10.1002/hbm.23594. Epub 2017 Apr 8. PMID: 28390148; PMCID: PMC6867148.

Aneurysmal Subarachnoid Hemorrhage Guidelines

Aneurysmal Subarachnoid Hemorrhage Guidelines

https://www.ahajournals.org/doi/full/10.1161/str.0b013e3182587839

Connolly ES Jr, Rabinstein AA, Carhuapoma JR, Derdeyn CP, Dion J, Higashida RT, Hoh BL, Kirkness CJ, Naidech AM, Ogilvy CS, Patel AB, Thompson BG, Vespa P; American Heart Association Stroke Council; Council on Cardiovascular Radiology and Intervention; Council on Cardiovascular Nursing; Council on Cardiovascular Surgery and Anesthesia; Council on Clinical Cardiology. Guidelines for the management of aneurysmal subarachnoid hemorrhage: a guideline for healthcare professionals from the American Heart Association/american Stroke Association. Stroke. 2012 Jun;43(6):1711-37. doi: 10.1161/STR.0b013e3182587839. Epub 2012 May 3. PubMed PMID: 22556195 1).

Hospital Characteristics and Systems of Care

According to current Aneurysmal Subarachnoid Hemorrhage Guidelines (aSAH) patients are mostly managed in intensive care units (ICU) regardless of baseline severity.

Low-volume hospitals (eg, <10 aSAH cases per year) should consider early transfer of patients with aSAH to high-volume centers (eg, >35 aSAH cases per year) with experienced cerebrovascular surgeons, endovascular specialists, and multidisciplinary neuro-intensive care services (Class I; Level of Evidence B). (Revised recommendation from previous guidelines)

Annual monitoring of complication rates for surgical and interventional procedures is reasonable (Class IIa; Level of Evidence C). (New recommendation)

A hospital credentialing process to ensure that proper training standards have been met by individual physicians treating brain aneurysms is reasonable (Class IIa; Level of Evidence C). (New recommendation) 2).


The adjusted odds of definitive repair were significantly higher in urban teaching hospitals than in urban nonteaching hospitals (odds ratio, 1.62) or rural hospitals (odds ratio, 3.08).7 In another study from 1993 to 2003, teaching status and larger hospital size were associated with higher charges and longer stay but also with better outcomes (P<0.05) and lower mortality rates (P<0.05), especially in patients who underwent aneurysm clipping (P<0.01). Endovascular treatment, which was more often used in the elderly, was also associated with significantly higher mortality rates in smaller hospitals (P<0.001) and steadily increasing morbidity rates (45%). Large academic centers were associated with better results, particularly for surgical clip placement 3).


Llull et al. from a Comprehensive Stroke Center in Barcelona assessed the prognostic and economic implications of initial admission of low-grade aSAH patients into a Stroke Unit (SU) compared to initial ICU admission.

They reviewed prospectively registered data from consecutive aSAH patients with a WFNS grade lower than 3 admitted at a Comprehensive Stroke Center between April-2013 and September-2018. Clinical and radiological baseline traits, in-hospital complications, length of hospital stay (LOS) and poor outcome at 90 days (modified Rankin Scale >2) were compared between the ICU and SU groups in the whole population and in a propensity score matched cohort.

From 131 patients, 74 (56%) were initially admitted in the ICU and 57 (44%) in the SU. In-hospital complication rates were similar in the ICU and SU groups and included rebleeding (10% vs 7%, p=0.757), angiographic vasospasm (61% vs 60%, p=0.893), delayed cerebral ischemia (12% vs 12%, p=0.984), pneumonia (6% vs 4%, p=0.697) and death (10% vs 5%, p=0.512). LOS did not differ across both groups [median (IQR) 22 (16-30) vs 19 (14-26) days, p=0.160]. In adjusted multivariate models, the location of initial admission was not associated with long-term poor outcome either in the whole population (OR=1.16, 95%CI=0.32-4.19, p=0.825) or in the matched cohort (OR=0.98, 95%CI=0.24-4.06, p=0.974).

A dedicated SU cared by a multidisciplinary team might be an optimal alternative to ICU to initially admit patients with low-risk aSAH 4).


Bederson JB, Connolly ES Jr, Batjer HH, Dacey RG, Dion JE, Diringer MN, Duldner JE Jr, Harbaugh RE, Patel AB, Rosenwasser RH; American Heart Association. Guidelines for the management of aneurysmal subarachnoid hemorrhage: a statement for healthcare professionals from a special writing group of the Stroke Council, American Heart Association. Stroke. 2009 Mar;40(3):994-1025. doi: 10.1161/STROKEAHA.108.191395. Epub 2009 Jan 22. Review. Erratum in: Stroke. 2009 Jul;40(7):e518. PubMed PMID: 19164800. 5).

References

1) , 2)

Connolly ES Jr, Rabinstein AA, Carhuapoma JR, Derdeyn CP, Dion J, Higashida RT, Hoh BL, Kirkness CJ, Naidech AM, Ogilvy CS, Patel AB, Thompson BG, Vespa P; American Heart Association Stroke Council; Council on Cardiovascular Radiology and Intervention; Council on Cardiovascular Nursing; Council on Cardiovascular Surgery and Anesthesia; Council on Clinical Cardiology. Guidelines for the management of aneurysmal subarachnoid hemorrhage: a guideline for healthcare professionals from the American Heart Association/american Stroke Association. Stroke. 2012 Jun;43(6):1711-37. doi: 10.1161/STR.0b013e3182587839. Epub 2012 May 3. PubMed PMID: 22556195.
3)

Andaluz N, Zuccarello M. Recent trends in the treatment of cerebral aneurysms: analysis of a nationwide inpatient database. J Neurosurg. 2008 Jun;108(6):1163-9. doi: 10.3171/JNS/2008/108/6/1163. PMID: 18518722.
4)

Llull L, Mayà G, Torné R, Mellado R, Renú A, López-Rueda A, Laredo C, Culebras D, Ferrando C, Blasco J, Amaro S, Chamorro Á. Stroke Units could be a valid alternative to Intensive Care Units for low-grade aneurysmal subarachnoid haemorrhage patients. Eur J Neurol. 2020 Sep 22. doi: 10.1111/ene.14548. Epub ahead of print. PMID: 32961609.
5)

Bederson JB, Connolly ES Jr, Batjer HH, Dacey RG, Dion JE, Diringer MN, Duldner JE Jr, Harbaugh RE, Patel AB, Rosenwasser RH; American Heart Association. Guidelines for the management of aneurysmal subarachnoid hemorrhage: a statement for healthcare professionals from a special writing group of the Stroke Council, American Heart Association. Stroke. 2009 Mar;40(3):994-1025. doi: 10.1161/STROKEAHA.108.191395. Epub 2009 Jan 22. Review. Erratum in: Stroke. 2009 Jul;40(7):e518. PubMed PMID: 19164800.

Postoperative pain

Postoperative pain

Perioperative pain assessment and management in neurosurgical patients varies widely across the globe. There is lack of data from developing world regarding practices of pain assessment and management in neurosurgical population.

A survey aimed to capture practices and perceptions regarding perioperative pain assessment and management in neurosurgical patients among anesthesiologists who are members of the Indian Society of Neuroanaesthesiology and Critical Care (ISNACC) and evaluated if hospital and pain characteristics predicted the use of structured pain assessment protocol and use of opioids for postoperative pain management.

A 26-item English language questionnaire was administered to members of ISNACC using Kwiksurveys platform after ethics committee approval. This outcome measures were adoption of structured protocol for pain assessment and opioid usage for postoperative pain management.

The response rate for this survey was 55.15% (289/524). One hundred eighteen (41%) responders informed that their hospital setup had a structured pain protocol while 43 (15%) responders reported using opioids for postoperative pain management. Predictors of the use of structured pain protocol were private setup (odds ratio [OR] 2.64; 95% confidence interval [CI] 1.52-4.59; p=0.001), higher pain intensity (OR 0.37; 95% CI 0.21-0.64; p<0.001) and use of pain scale (OR 7.94; 95% CI 3.99-15.81; p<0.001) while availability of structured pain protocol (OR 2.04; 95% CI 1.02-4.05; p=0.043) was the only significant variable for postoperative opioid use.

Less than half of the Indian neuroanesthesiologists who are members of ISNACC use structured protocol for pain assessment and very few use opioids for postoperative pain management in neurosurgical patients 1).


Studying the characteristics of postoperative pain at such an early stage allows for improved management. It helps to predict, according to the type of surgery and the anaesthesia used, those patients in which higher VAS values may be seen and to better adapt analgesic therapy 2).

Despite advances in surgical and anesthesiology techniques, many patients continue to experience postoperative pain after lumbar disc operations

The administration of tramadol with paracetamol was more effective than tramadol alone for early acute postoperative pain therapy following lumbar discectomy. Therefore while adding paracetamol in early pain management is recommended, continuing paracetamol for the late postoperative period is not advised 3).

Etiology

Epidural fibrosis and epidural adhesion after laminectomy are developed from adjacent dense scar tissue, which is a natural wound healing process 4) 5) 6) 7) , and ranked as the major contributor for postoperative pain recurrence after laminectomy or discectomy.

Treatment

The goal of postoperative pain management is to relieve pain while keeping side effects to a minimum. After hundreds of years of advances, the mainstay of pain therapy is still the opioids. While they are very effective analgesics, opioids also carry with them many undesirable side effects: sedation, respiratory depression, nausea and vomiting, hypotension and bradycardia, pruritus, and inhibition of bowel function. The treatment of complications such as nausea and pruritus may include the administration of antihistamines, which have an additive effect on sedation and respiratory depression.

References

1)

Sriganesh K, Bidkar PU, Krishnakumar M, Singh GP, Hrishi AP, Jangra K. Perioperative Analgesia In Neurosurgery (PAIN): A national survey of pain assessment and management among neuroanesthesiologists of India. Int J Clin Pract. 2020 Sep 23:e13718. doi: 10.1111/ijcp.13718. Epub ahead of print. PMID: 32966673.
2)

Cabedo N, Valero R, Alcón A, Gomar C. Prevalence and characterization of postoperative pain in the Postanaesthesia Care Unit. Rev Esp Anestesiol Reanim. 2017 Mar 28. pii: S0034-9356(16)30211-0. doi: 10.1016/j.redar.2016.11.006. [Epub ahead of print] English, Spanish. PubMed PMID: 28363327.
3)

Uztüre N, Türe H, Keskin Ö, Atalay B, Köner Ö. Comparison of Tramadol versus Tramadol with Paracetamol for efficacy of postoperative pain management in lumbar discectomy: a randomized controlled study. Int J Clin Pract. 2019 Sep 11. doi: 10.1111/ijcp.13414. [Epub ahead of print] PubMed PMID: 31508863.
4)

Alkalay RN, Kim DH, Urry DW, Xu J, Parker TM, Glazer PA. Prevention of postlaminectomy epidural fibrosis using bioelastic materials. Spine (Phila Pa 1976) 2003;28:1659–1665.
5)

Hsu CJ, Chou WY, Teng HP, Chang WN, Chou YJ. Coralline hydroxyapatite and laminectomy-derived bone as adjuvant graft material for lumbar posterolateral fusion. J Neurosurg Spine. 2005;3:271–275.
6)

Temel SG, Ozturk C, Temiz A, Ersozlu S, Aydinli U. A new material for prevention of epidural fibrosis after laminectomy: oxidized regenerated cellulose (interceed), an absorbable barrier. J Spinal Disord Tech. 2006;19:270–275.
7)

Yu CH, Lee JH, Baek HR, Nam H. The effectiveness of poloxamer 407-based new anti-adhesive material in a laminectomy model in rats. Eur Spine J. 2012;21:971–979.
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