[1] Defendant has brought forward eight arguments on appeal. All eight address one issue, the evidence and proof of damages, particularly the evidence and proof of damages relating to the preexisting syringomyelia. Our State recognizes the “special sensitivity” or “thin skull” rule. According to this rule, a negligent defendant is subject to liability for harm to the plaintiff although a physical condition of plaintiff which is neither known nor should be known to defendant makes the injury greater than that which defendant as a reasonable man should have foreseen as a probable result of his conduct. Restatement of Torts 2d § 461 (1965). As stated by our Supreme Court.
[t]he general rule is that if the defendant’s act would not have resulted in any injury to an ordinary person, he is not liable for harmful consequences to one of peculiar susceptibility, except insofar as he was on notice of the existence of such susceptibility, but if his misconduct amounts to a breach of duty to a person of ordinary susceptibility, he is liable for all damages suffered by plaintiff notwithstanding the fact these damages are unusually extensive because of peculiar susceptibility.
Lockwood v. McCaskill, 262 N.C. 663, 670, 138 S.E. 2d 541, 546 (1964). This case is but an application of this rule to a case where a preexisting condition has been aggravated. Plaintiff has presented competent medical evidence that his preexisting syrin-gomyelia was aggravated by the collision which resulted from the negligence of defendant. Defendant is liable for the damages due to enhancement or aggravation of the condition.
An injured person is entitled to recover all damages proximately caused by the defendant’s negligence. Even *551so, when his injuries are aggravated or activated by a preexisting physical or mental condition, defendant is liable only to the extent that his wrongful act proximately and naturally aggravated or activated plaintiffs condition. “The defendant is not liable for damages ... attributable solely to the original condition.”
Potts v. Howser, 274 N.C. 49, 54, 161 S.E. 2d 737, 742 (1968). We now deal with the separate arguments of defendant addressed to this general principle of liability for the resulting damages.
[2] Defendant questions evidence of certain medical bills and expenses which plaintiff incurred. Over his objection, the trial court admitted testimony about a $1,511.06 bill for hospitalization in August 1976 and clinic treatment costs related to this hospitalization of $740.00 to his doctors and $57.00 to urologists. Defendant contends no competent medical testimony or evidence was presented by plaintiff to show that those medical bills were for treatment of injuries suffered as a result of defendant’s negligence. Such evidence relating the damages to the injury caused by the defendant is required. Ward v. Wentz, 20 N.C. App. 229, 201 S.E. 2d 194 (1973); Graves v. Harrington, 6 N.C. App. 717, 171 S.E. 2d 218 (1969). Defendant points to the testimony of Dr. Weng where in discussing the August 1976 hospitalization he said, “the reason for the hospitalization in August of 1976 ... had nothing to do with the cervical sprain he received in the accident and this was to establish whether he did or did not have syringomyelia and that was the sole purpose of that hospitalization.” This does not indicate as defendant contends that these medical costs are not damages for which defendant was liable. Plaintiffs case was based on damages which arose from the accident in two forms — a cervical sprain and aggravation of his syringomyelia. Thus, hospitalization costs in August 1976 following the accident to determine whether plaintiff indeed had syringomyelia were competent evidence of plaintiffs damages resulting from the accident.
[3] Defendant contends the trial court committed error in permitting plaintiff s evidence of why plaintiff and his wife stopped teaching, of bladder problems, of salary since the 1976 accident, of days missed from his teaching job and of pain and suffering *552and mental anguish since the 1976 accident. He contends there is no causal connection between this testimony and the injuries suffered in the 1976 collision and that these items are in effect items of special damages not specifically pled by plaintiff as required by our Rules of Civil Procedure. G.S. 1A-1, Rule 9(g). The objected to evidence is directly related to the worsening syringomyelia for which defendant is liable to the extent his negligent conduct aggravated the preexisting condition. Potts v. Howser, supra; Howell v. Nichols, 22 N.C. App. 741, 207 S.E. 2d 768, cert. den., 286 N.C. 211, 209 S.E. 2d 316 (1974). The expert testimony on causation of Dr. Weng and Dr. Price, is in conflict. The testimony presented a jury question and, if the jury chose to take Dr. Weng’s opinion on the relationship of the worsened state of plaintiffs preexisting degenerative disease to the 1976 accident over that of Dr. Price, this evidence is causally related to the 1976 accident. According to Dr. Weng,
If a patient has syringomyelia in the area where the cord is swollen up in its sheath, it will increase pressure and it will cause further extension of the canal. It will be like increasing a jet of water on the river bank and it will wash away more of the soil of the river bank and so the whiplash injury can or could aggravate the problem. It may hasten the development of fresh-worsening of neurological signs.
He went on to say that the accident could have aggravated the syringomyelia. His testimony to this effect is not too speculative as defendant contends. The doctor also testified that the collision could or might have caused a permanent cervical sprain. The evidence objected to is lay testimony supported by competent expert testimony tending to prove damages resulting from the accident. We find no merit to defendant’s contention that these damages were not adequately pled by plaintiff. Plaintiff alleged that he “suffered extensive injuries, great pain of the body and mind, was prevented from transacting his business and incurred expenses for medical attention, hospitalization and damages to his person in an amount not yet determined.” A subsequent amendment alleged damages to be $75,000.00. This is sufficient specific pleading under our Rules of Civil Procedure of these damages for which proof was offered. See also Sparks v. Holland, 209 N.C. 705, 184 S.E. 552 (1936).
*553 [4] Defendant contends the hypothetical question to Dr. Weng contained facts not supported by competent evidence and that the opinion of Dr. Weng was based on speculation about medical possiblility as opposed to reasonable certainty or probability. The hypothetical question was acceptable in that it included only facts in evidence or which the jury might logically infer from the evidence. Thompson v. Lockhert, 34 N.C. App. 1, 237 S.E. 2d 259, cert. den., 293 N.C. 593, 239 S.E. 2d 264 (1977). The response of Dr. Weng was not so speculative as to be inadmissible as competent evidence of causation. The case at hand is factually distinguishable from Garland v. Shull, 41 N.C. App. 143, 254 S.E. 2d 221 (1979) which is relied upon by defendant. The testimony of the medical expert in Garland in response to a hypothetical question was, “The headaches may persist for years at least. An indefinite period of time.” Id. at 147, 254 S.E. 2d at 223 (emphasis added). The Court held the admission of this doctor’s opinion with regard to possible pain and suffering which plaintiff might suffer in the future to be error. There was no amplification or explanation of the expert opinion in Garland. Dr. Weng, in the case at hand, stated that he was speaking of what was medically possible and what will happen. On cross-examination, he stated that “it would be less likely” that the accident would not have aggravated the syringomyelia. The evidence in the case at hand goes far beyond that offered in Garland. As stated by our Supreme Court in Lockwood,
[t]he opinion is based on the reasonable probabilities known to the expert from scientific learning and experience. A result in a particular case may stem from a number of causes. The expert may express the opinion that a particular cause “could” or “might” have produced the result — indicating that the result is capable of proceeding from the particular cause as a scientific fact, i.e., reasonable probability in the particular scientific field. If it is not reasonably probable, as a scientific fact, that a particular effect is capable of production by a given cause, and the witness so indicates, the evidence is not sufficient to establish prima facie the causal relation, and if the testimony is offered by the party having the burden of showing the causal relation, the testimony, upon objection, should not be admitted and, if admitted, should be stricken. The trial judge is not, of *554course, required to make subtle and refined distinctions and he has discretion in passing on the admissibility of expert testimony, and if in the exercise of his discretion it reasonably appears to him that the expert witness, in giving testimony supporting a particular causal relation, is addressing himself to reasonable probabilities according to scientific knowledge and experience, and the testimony per se does not show that the causal relation is merely speculative and mere possibility, the admission of the testimony will not be held erroneous.
Id. at 262 N.C. at 668-69, 138 S.E. 2d at 545-46. The testimony of Dr. Weng satisfies the prerequisites for expert opinion set forth in Lockwood.
Defendant’s remaining arguments are without merit. Amendment of the complaint at the close of the evidence to conform to the proof was properly allowed by the trial court. G.S. 1A-1, Rule 15(b). The jury instructions were proper in all respects, particularly the instructions on damages for aggravation of a preexisting injury wherein the instruction complied with the law in Lockwood and Potts v. Howser. The trial court properly denied defendant’s motion for a new trial.
No error.
Judges Parker and Hedrick concur.