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Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominantly inherited colorectal cancer syndrome attributable to mutations in one of several DNA mismatch repair genes, most commonly MLH1 and MSH2 . In certain populations, founder mutations account for a substantial portion of HNPCC. In this report we summarize the literature and our personal experience testing for a specific founder mutation in the Ashkenazi Jewish population, MSH2*1906G > C , also known as A636P. Although rare in the general population, the A636P mutation is detected in up to 7% of Ashkenazi Jewish patients with early age-of-onset colorectal cancer, and may account for up to one third of HNPCC in the Ashkenazi Jewish population. In addition, we summarize our initial experience with a prospective A636P testing protocol aimed at Ashkenazi Jewish patients at high or intermediate risk for harboring the A636P mutation.

fig. 7), 53 (fig. 8) and 85 were school teachers who had been forced to give up their profession on account of their hearing impairment. They have all regained their positions and are now teaching school.When the postoperative hearing level is raised to within 20 decibels of normal for the speech frequencies the patient will have sufficient hearing to be regarded as normal under practically all circumstances. For example, patients 38 (fig.. 9) and 59 (fig. 10) were passed by their Selective Service draft board as having "normal" hearing six months after the fenestration.When the postoperative hearing level is raised to within 30 decibels of normal the patient will be able to get along without difficulty in the majority of social and economic contacts. Of the 117 patients operated on the hearing loss has been restored to within 20 decibels of normal for the speech frequencies in 11 and to within 30 decibels of normal for speech in 52. COMPLICATIONSIncluding the 19 patients who had revisions and the 11 who had both ears operated on, a total of 147 con¬ secutive operations were done on the 117 patients, with no fatalities and no serious complications. Minor com¬ plications in this series have consisted of transient facial paralysis in 4 cases beginning seven to ten days after the operation, with complete recovery in each case within one to two weeks ; postoperative pulmonary atelectasis in 1 case which cleared promptly on change of position (seating the patient in a chair), hyperventilation with carbon dioxide and forced coughing.Postoperative sterile labyrinthitis of varying degree is the rule after fenestration and is evidenced by dizzi¬ ness, nystagmus, ataxia and depression in hearing last¬ ing a few days to a week. In 2 of the 117 cases the hearing depression was permanent, amounting to a further loss of 18 decibels for the speech frequencies in 1 case and 13 decibels in the other. Since in each case the poorer hearing ear had been selected for oper¬ ation, this further loss was not of serious consequence to the patient's useful hearing. In 2 other patients the dizziness has lasted in a mild form for more than a year, consisting of a sense of unbalance on sudden move¬ ments. As a rule the dizziness and ataxia disappear completely within the first three or four weeks after operation. SUMMARY AND CONCLUSIONS 1. The fenestration operation offers the possibility of the partial restoration of impaired hearing, the result of stapes fixation.2. The problem of the closure of the new window has been largely solved by the technic now being used.3. The hearing after a successful fenestration oper¬ ation generallv surpasses that secured with a hearing aid (figs. 11 and 12).4. The fenestration operation is not always success¬ ful, and the hearing may be made worse in the operated ear.For this reason the poorer hearing ear should always be selected for operation. 5. A hearing improvement maintained for more than six months after fenestration may be regarded as probably permanent.6. Properly done, the fenestration operation ...

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