The modern, evidence-based medicine requests an increasing demand for quality management. The improvement of quality, in great part, depends on the assessment of negative outcomes. Surgical complications are a major factor in increasing the costs of healthcare [9, 16]. The need for a classification of complications approved by the scientific community, allowing a comparison of different series of patients, is widely advocated in the neurosurgical society [2, 14].
Despite many trials, the definition of "surgical complication" remains controversial in some scientific groups [2, 5, 8, 14, 22, 24]. The current contention point in the neurosurgical society seems to be the "sequelae" [2, 4]. According to the oxford dictionary, "sequelae" is defined as "A condition which is the consequence of a previous disease or injury." [18]. In general surgery, a "sequelae" is defined as an "after-effect" of surgery, for example, an "inability to walk after an amputation of the leg" [8]. In consideration of the above-mentioned, Clark and Spetzler suggested that any, because of surgery complexity expected, postoperatively occurred neurological disturbances should not be assessed as a complication [4]. "For example, a hemiparesis occurring to a patient operated for a large arteriovenous malformation (AVM) located in the motor cortex will be classified as a sequela, whereas the same neurological deficit occurring after the removal of a frontal AVM reaching the Silvian fissure (secondary, that is, to coagulation of a middle cerebral artery branch feeding the corticospinal bundle) should be considered as a complication" [2].
This example of AVM surgery does not seem to be fully comparable to the amputation of the leg. Because of the complexity of the brain's functional structure, there is almost impossible to surely predict the exact extend of postoperative neurological deficits, like the result of leg amputation, excluding the so-called "awake brain surgery" or lobotomy after fiber tracking. However, the evaluation of postoperative occurred expected disturbances seems to be clearly more oriented to self-development and improvement of quality than a camouflage of postoperative occurred neurological deficits under the term of "sequelae."
Obviously, fairness can not involve a direct comparison between the outcomes of AVM and Meningioma surgery, or procedures in eloquent and non-eloquent areas. For this purpose, an additional detailed ranking system of the complexity of neurosurgical procedures could help.
The earlier classifications of surgical complications, which have been applied in neurosurgery, were oriented to the general surgical complications and the treatments necessary to treat them, disregarding the neurological disturbances similar to general surgery [2, 14, 15]. The main difference between neurosurgery and other surgical disciplines is surely the frequency and variety of postoperative neurological disturbances. In principle, the severity of postoperative occurred neurological symptoms frequently defines the outcome of neurosurgical treatment and the patient's quality of life.
Creating the CPNC were discussed several designs of ranking system assessing the postoperative neurological complications:
- A precise ranking system describing every functional or mental ability of patients and summarizing them in numerical parameters pre-and postoperatively gave a concrete score of worsening of concrete neurological deficit. Still, it did not show an influence of the complication on the affected patient's limitations in daily life. Such classification also seemed to be too multifactorial and complex for use in daily clinical practice.
- A classification concentrating only on daily life activities of patients, similar to the "Karnofsky index" or "SF-36," seemed to be too imprecise describing the neurological disturbances and gave no possibility for ranking the slight neurological deficits. For example, a postoperatively occurred, left-sided L5 - hypesthesia or peroneal palsy by a patient with high-grade hemiparesis on the same side preoperatively, would not cause any additive restriction of daily life activities. Consequently, these complications would be ignored by such a ranking system.
- A ranking system based on the treatments necessary to treat the complications appeared to be neglected for the end results of neurosurgical procedures. The inadequacy of such classifications to rank the neurosurgical complications has been already reported in the literature [2, 20].
Regarding the above mentioned, on the one hand, if we consider the great variety of possible postoperative disturbances, there is an obvious need to generalize or uniting them corresponding to functional restriction to make the classification reproducible and practicable in daily clinical practice. On the other hand, the type, severity, and persistence of neurological complications seems to be also very important to assess the outcome of neurosurgical procedures.
Consequently, the CPNC, as a classification based on type, persistence, and severity of postoperative occurred neurological complications and, at the same time, generalizing them into functional restrictions, seems to have an opportunity of success.
An attempt to validate the new proposal of classification by correlating the grades of complications with the severity of postoperative neurological disturbances was made in a cohort of 1530 patients. The assessed 1680 operations included all sections of the nervous system. Every recorded neurological complication could be easily classified according to the CPNC. The correlation between the CPNC grades and the length of hospital stay, as "a useful parameter of the severity of a complication" [6, 8, 9], was evident in this article. The simpleness and reproducibility of the proposed classification was statistically validated by the "almost perfect" agreement between the raters with k= 0,94 (Cohen's kappa coefficient).
Obviously, the fact that improvement of neurological disturbances can take a long time [11, 25] and the neurological state at the time of discharge from acute care hospital mostly is not a final result, leads to the requirement of evaluation of neurological state after completed rehabilitation. For this purpose, the suggested suffix "r" appears to be useful for observation of neurological complications in the follow-up period and determination of the final outcome.
With a goal of success for the proposed classification, it is necessary to be approved by the scientific community. For this purpose should be undertaken further multicentral and preferable international studies.
We can recommend the CPNC as an easily applicable and comparable instrument in the quality management of every main and sub-specialties of neurosurgery. The broad implementation of this classification into neurosurgical literature may facilitate the evaluation and comparison of outcomes among different surgeons, centers, and therapies.
With a goal of success for the proposed classification, it is necessary to be approved by the scientific community. For this purpose should be undertaken further multicentral and preferable international studies.