This is an appeal from an Order in the Court of Common Pleas of Philadelphia County dated May 14, 1986, denying Riddle Memorial Hospital’s motion for a new trial and judgment n.o.v.
The lawsuit that is the basis of this appeal arose out of a medical malpractice claim commenced by Nancy F. Mitzelfelt and her husband. In her complaint, Mrs. Mitzelfelt alleged medical negligence in connection with a neurosurgical procedure performed by Dr. Robert Kamrin at appellant Riddle Memorial Hospital. Also named in her suit were Dr. Robert Andre, Dr. Kamrin’s co-practitioner; Neurological Associates, a professional corporation composed of the two doctors; and Riddle Memorial Hospital, whose negligence allegedly flowed from the acts of its agents administering the anesthesia. Riddle, in turn, cross-claimed against Drs. Kamrin and Andre, alleging that Mrs. Mitzelfelt’s injuries were the result of the negligence of its co-defendants and not the result of any negligence on the part of the hospital or its agents. As a result of her surgery, Mrs. Mitzelfelt now suffers from quadriparesis, a weakening of her extremities.
Pretrial discovery revealed two possible causes for Mrs. Mitzelfelt’s injuries: an uncorrected drop in blood pressure during surgery which cut off the blood flow to the spinal cord; and the positioning of the head of the patient during surgery. The first theory implicated the conduct of those medical personnel providing the anesthesia. The second implicated the surgeons who performed the procedure.
*124On the first day of trial, Dr. Kamrin, the Estate of Dr. Andre and Neurological Associates settled with and obtained a joint tortfeasor release from the Mitzelfelts. Consequently, counsel for the Mitzelfelts presented no expert testimony to establish negligence on the part of the surgeons. The Mitzelfelts did, however, call as their sole liability expert Dr. Henry Shenkin, who they had not previously named as an expert in their pretrial memoranda, but who was the expert of the defendant surgeons. The testimony of Dr. Shenkin revolved around a small portion of a report he prepared prior to trial which referred to the issue of anesthesia and the potential liability of Riddle. At the close of Plaintiffs’ case, all Defendants moved for a compulsory non-suit and were denied. At the close of all the evidence at trial, the court, on the motion of the defendant surgeons entered a directed verdict in their favor, finding that there was no evidence of negligence against them as a matter of law. As against Riddle, the jury returned a verdict in favor of the Mitzelfelts in the amount of $3,000,-000. 00 which was subsequently molded to include delay damages. Riddle then filed timely post-trial motions, which were denied. The trial court entered judgment on the verdict and this appeal by Riddle followed. We reverse.
The question presented in this case is whether the appellees presented the competent expert testimony required to establish a prima facie case of medical malpractice. Resolution of this question is dependent upon whether the plaintiff’s expert, Dr. Shenkin, expressed an opinion with sufficient certainty with respect to the cause of Mrs. Mitzelfelt’s condition to allow the case to go to the jury. Because our review of the record reveals that Dr. Shenkin’s opinion as to causation did not rise to the level of certitude necessary to constitute legally competent evidence, we find that the appellees failed to present a prima facie case of medical malpractice and accordingly reverse the judgment of the trial court.1
*125As a preliminary matter we address appellees’ contention that Riddle has waived this issue for purposes of appeal. In its post-trial motions Riddle set forth this claim as follows:
The trial court erred in refusing to grant a non-suit at the conclusion of plaintiff’s case, where the only expert testimony offered by the plaintiffs on the question of negligence and causation was from Dr. Henry Shenkin, and where Dr. Shenkin testified that he could not say, within a reasonable degree of medical certainty, that a drop in blood pressure caused Nancy Mitzelfelt’s paralysis.
The Mitzelfelts claim that Riddle has waived its challenge to the trial court’s failure to grant a compulsory non-suit when it elected to put on its defense. In support of this proposition the Mitzelfelts cite Burns v. City of Philadelphia, 350 Pa.Super. 615, 504 A.2d 1321 (1986). In Burns we stated:
A compulsory nonsuit can be granted at the close of plaintiff’s case and before the defense presents any evidence. If the defendant elects to proceed, the non-suit stage is over and the correctness of the court’s ruling is moot.
Id., 350 Pa.Superior Ct. at 623, 504 A.2d at 1325.
Because the defendant in Burns elected to present its case after the plaintiff had rested, we refused to address the propriety “of the motion for compulsory non-suit as such.” Id. However, we went on to address the underlying arguments in support of the motion for non-suit as arguments in support of the defendant’s motion for judgment n.o.v. Id. Here too, as in Burns, we will treat Riddle’s underlying claim of error as an argument in support of its motion for judgment n.o.v.
The standard of review that we employ in considering the propriety of an order granting or denying judgment n.o.v. is the same as the trial court’s: the appellate court must determine whether there was sufficient competent evidence to sustain the verdict, granting the verdict winner the benefit of every reasonable inference which can reasonably be drawn from the evidence and rejecting all unfavorable *126testimony and inferences. Judgment n.o.v. may be granted only in a clear case where the facts are such that no two reasonable minds could fail to agree that the verdict was improper. Ingrassia Construction Company, Inc. v. Walsh, 337 Pa.Super. 58, 61, 486 A.2d 478, 480 (1984).
Riddle contends that the verdict was improper because the plaintiffs failed to meet their burden of proof. More specifically, Riddle argues that there was insufficient competent expert testimony for the issue of causation to be submitted to the jury. The general rule in this Commonwealth is that in order to establish a cause of action for medical malpractice, the plaintiff must present expert testimony establishing variance from accepted medical practice and that this deviation from community standards caused the plaintiffs injuries. Brannan v. Lankenau Hospital, 490 Pa. 588, 417 A.2d 196 (1980); Hamil v. Bashline, 481 Pa. 256, 267, 392 A.2d 1280, 1285 (1978); Denardo v. Carneval, 297 Pa.Super. 484, 489, 444 A.2d 135, 137 (1982). The only exception to the general requirement that expert testimony must be produced is “where the matter under investigation is so simple, and the lack of skill or want of care so obvious, as to be within the range of ordinary experience and comprehension of even nonprofessional persons.” Chandler v. Cook, 438 Pa. 447, 451, 265 A.2d 794, 796 (1970), citing Smith v. Yohe, 412 Pa. 94, 194 A.2d 167 (1963). The present case is one which falls under the general rule requiring expert testimony since questions as to the cause of Mrs. Mitzelfelf s quadriparesis are beyond the knowledge of the average layperson.2
As in other negligence cases, the plaintiff in a medical malpractice case bears the burden of proving a causal *127nexus between the wrongful conduct and the injury as part of the prima facie case. The plaintiffs “burden of proof” on this issue encompasses two separate and distinct burdens. C. McCORMICK, HANDBOOK OF THE LAW OF EVIDENCE § 336, at 947 (3d ed. 1984). The first burden, the burden of production, refers to the responsibility of the plaintiff to present evidence of sufficient quality and weight that reasonably intelligent men could believe in the existence of the causal link sought to be established. If the plaintiff fails to satisfy this initial burden, it becomes incumbent upon the trial judge to remove the issue from consideration by the jury, since any decision reached by the jury based on consideration of this evidence would involve an inordinate amount of speculation and conjecture. W. PROSSER, HANDBOOK OF THE LAW OF TORTS § 37, at 205 (4th ed. 1971). If the plaintiff succeeds in presenting evidence of sufficient quality and weight so that the evidence is allowed to reach the jury, he or she must then satisfy the second burden, the burden of persuasion. The burden of persuasion involves convincing the jury that the preponderance of the evidence shows defendant’s conduct to have been a substantial cause of the harm to the plaintiff. Hamil, supra 481 Pa. at 265, 392 A.2d at 1284.
The yardstick by which it is determined whether the expert testimony presented by the plaintiff is of a sufficient quality and weight so as to be proper evidence for jury consideration is “reasonable medical certainty.”3 See Jones v. Montefiore Hospital, 494 Pa. 410, 431 A.2d 920 *128(1981); Gradel v. Inouye, 491 Pa. 534, 421 A.2d 674 (1980). Although the expert need not express his opinion in the same language that we use to enunciate the legal standard, the opinion, taken in its entirety, must demonstrate reasonable certainty that the result in question came from the cause alleged. Pirches v. General Accident Insurance Company, 354 Pa.Super. 303, 308, 511 A.2d 1349, 1352 (1986); Kravinsky v. Glover, 263 Pa.Super. 8, 396 A.2d 1349 (1979). Perhaps the most authoritative expression of the rule, and the policy reasons behind it, was set forth by our supreme court in McMahon v. Young, 442 Pa. 484, 276 A.2d 534 (1971). In McMahon, the physician testified that there was “probably a cause and effect relationship between the accident and the injury” and that the automobile accident was “consistent with that sort of injury.” In finding the physician’s testimony did not constitute legally competent evidence, the court opined:
... [T]he expert has to testify, not that the condition of the claimant might have, or even probably did, come *129from the accident, but that in his professional opinion the result in question came from the cause alleged. A less direct expression of opinion falls below the required standard of proof and does not constitute legally competent evidence ...
The issue is not merely one of semantics. There is a logical reason for the rule. The opinion of a medical expert is evidence. If the fact finder chooses to believe it, he can find as fact what the expert gave as an opinion. For a fact finder to award damages for a particular condition to a plaintiff it must find as a fact that that condition was legally caused by the defendant’s conduct. Here, the only evidence offered was that it was “probably” caused, and that is not enough. Perhaps in the world of medicine nothing is absolutely certain. Nevertheless, doctors must make decisions in their own profession every day based on their own expert opinions. Physicians must understand that it is the intent of our law that if the plaintiff’s medical expert cannot form an opinion with sufficient certainty so as to make a medical judgment, there is nothing on the record with which the jury can make a decision with sufficient certainty so as to make a legal judgment.
Id,., 442 Pa. at 486, 276 A.2d at 535. Consequently, if the plaintiff’s expert’s testimony does not convey the requisite confidence, the jury will not be permitted to consider the evidence and speculate on the issue of causation.4 It is only when the physician demonstrates reasonable certitude in his opinion that the expert testimony can be said to aid the trier of fact in resolving the ultimate issue of causation.
In the present case, the “target” defendants were Dr. Kamrin, the surgeon who performed the operation, Dr. Andre, his partner, and the professional corporation composed of the two doctors. The theory under which the plaintiff’s asserted that the surgeons were liable was that *130Dr. Kamrin negligently positioned Mrs. Mitzelfelt’s head and neck during the operation which allegedly resulted in her quadriparesis. On the day that trial was scheduled to commence, Dr. Kamrin, the Estate of Dr. Andre, and Neurological Associates, settled with the Mitzelfelt’s and obtained a joint tortfeasor’s release. As a result, the plaintiffs presented no expert testimony with respect to the negligence of the surgeons. Instead, the plaintiffs proceeded on the theory that Riddle was liable because its ostensible agent, the anesthesiologist, negligently failed to maintain Mrs. Mitzelfelt’s blood pressure at a level which would facilitate blood flow to the spinal cord. The plaintiffs further claimed that the drop in blood pressure to 80/55 during the procedure caused Mrs. Mitzelfelt’s quadriparesis. In support of this contention, plaintiffs called Dr. Shenkin, who had previously been the expert of the defendant surgeons. On direct examination by plaintiff’s counsel, Dr. Shenkin testified as follows:
Q. Was it your opinion, and I assume any opinion you express is based upon your reasonable evaluation as a physician, isn’t that true?
A. Yes, sir.
Q. And your opinion that this drop in blood pressure is sufficient to compromise the blood supply to the spinal cord of this particular patient in the upright position and under general anesthesia. You said that opinion in this letter, did you not?
A. Yes, sir.
Q. And that is your opinion, is it not?
A. I think that is what I think, yes.
Q. That is what you said there?
A. That is my opinion, whatever that means, yes.
N.T. August 29, 1984, at 175. However, on cross examination by defense counsel Dr. Shenkin equivocated on his earlier opinion as to the cause of Mrs. Mitzelfelt’s condition:
Q. The bottom line is, do you know within a reasonable degree of medical certainty, can you tell the ladies and gentlemen of this jury within a reasonable degree of *131medical certainty that this drop in that blood pressure, that one reading to something between 85 and 90 millimeters of mercury caused the problem that Mrs. Mitzelfelt has?
A. No. It is my opinion that it could have, but I wouldn’t put it as a reasonable degree of medical certainty.
Q. I am asking you the question within a reasonable degree of medical certainty, can you say this drop, as you have testified to, caused Mrs. Mitzelfelt’s condition?
A. No, I can’t.
N.T. August 29, 1984, at 223-224 (emphasis added).
We believe that the totality of Dr. Shenkin’s testimony reflects his belief that the drop in Mrs. Mitzelfelt’s blood pressure during the operation “could have” caused her quadriparesis. A medical opinion that merely states that the cause alleged “could” lead to the condition in question does not rise to the level of certainty required to constitute competent evidence for jury consideration. See Kravinsky, supra, 263 Pa.Super. at 21, 396 A.2d at 1355. While it may be true that there was other evidence presented regarding the standard of care and breach of that standard which may have warranted submission of the question of negligence to the jury,5 the record is devoid of expert testimony, other than Dr. Shenkin’s, which could establish with reasonable certainty that Mrs. Mitzelfelt’s condition resulted from the drop in blood pressure. In short, the probabilities with respect to the causative agent were not sufficiently linked to the patient’s condition such that a jury determination on the issue would be shielded from the specter of undue speculation. As a result, we find that the plaintiffs failed to provide the competent medical evidence necessary to *132establish a material element of their prima facie case, namely, that conduct of the anesthesiologist caused Mrs. Mitzelfelt’s quadriparesis. Because there was insufficient competent evidence to sustain the jury’s verdict, we find that judgment n.o.v. was appropriate.
Accordingly, judgment is reversed.
TAMILIA, J., files a concurring and dissenting opinion.. Because of our resolution of this issue we need not address the other issues raised in appellant’s brief.
. We note that the present case is readily distinguishable from Brannan v. Lankenau Hospital, 490 Pa. 588, 417 A.2d 196 (1980), which has been relied upon by the dissent. In Brannan, our supreme court held that expert testimony was not necessary to establish that hospital staffs failure to notify the attending physician of a patient’s deteriorating condition was negligent conduct. Instantly, whether Mrs. Mitzelfelt’s present medical condition was caused by the conduct of the medical personnel who provided the anesthesia during her surgery is a complex medical question which requires the testimony of a qualified medical expert.
. There is a limited exception to the general rule requiring that the expert opinion demonstrate reasonable certainty with respect to the issue of causation. In Hamil v. Bashline, supra, our supreme court carved a narrow exception to the general rule to be applied in a limited context. In cases to which Section 323(a) of the Restatement (second) of Torts applies, the so called "lost chance cases”, the issue of causation may be submitted to the jury upon a lesser showing of certainty. Id., 481 Pa. at 269, 392 A.2d at 1288. The court stated:
Section 323(a) recognizes that a particular class of tort actions, of which this case is an example, differs from those cases normally sounding in tort. Whereas typically a plaintiff alleges that a defendant’s act or omission set in motion a force which resulted in harm, *128the theory of the present case is that the defendant’s act or omission failed in a duty to protect against harm from another source. To resolve such a claim a fact-finder must consider not only what did occur, but also what might have occurred, i.e., whether the harm would have resulted trom the independent source even if defendant had performed his service in a non-negligent manner. Such a determination as to what might have happened necessarily requires a weighing of probabilities.
Id. The court further reasoned that because fact patterns which fall within the confines of Section 323(a) "by their very nature elude the degree of certainty one would prefer and upon which the law normally insists before a person may be held liable", these cases will be permitted to go to the jury upon a showing that the defendant’s acts or omissions have "increased the risk of harm to the plaintiff." Id. In finding that a lower standard of proof was appropriate given the peculiar nature of such cases, the court in Hamil also noted its decision was not meant "to undermine the well-established standard of 'reasonable degree of medical certainty’ as the accepted norm for medical opinions on causation.” Thus, the Hamil exception to the normal degree of certitude required for expert testimony applies only to those medical malpractice cases in which "the harm resulting from the improper treatment or lack of treatment is difficult to distinguish from the harm which could result even given the best treatment.” See Note, Increased Risk of Harm: A New Standard for Sufficiency of Evidence of Causation in Medical Malpractice Cases, 65 B.U.L.Rev. 275 (1985).
. While the plaintiffs expert is required to express an opinion with reasonable medical certainty on the issue of causation, the defendant’s rebuttal expert on the issue need not express such certainty. See Neal v. Lu, 365 Pa.Super. 464, 530 A.2d 103 (1987).
. Several witnesses, including Dr. Shenkin, testified that it was the function of the anesthesiologist to monitor the patients blood pressure during the course of the operation. In addition, Nurse McGrath, a nurse anesthetist, testified that in her opinion it would be negligence to allow a patient’s blood pressure to fall to a level of 80/55 without taking corrective measures. Nurse McGrath did not testify, however, concerning her opinion of the cause of Mrs. Mitzelfelt’s quadriparesis.