April 2005

First, a correction: I’m sure you’ll agree that there are times when I really don’t know my right from my left. You may have thought one of those times was when I was writing the February column. In the discussion of tuberculin skin testing (TST), I stated that the test should be placed on the right arm, but in the picture my left arm was being used. Well, the picture is correct. At least at our clinic, we always use the volar surface of the LEFT arm for consistency. It’s the simple things that show how dumb we, I mean I really am at times. In a column many years ago I mistakenly referred to Brudzinski’s sign as Kernig’s sign. I got a lot of mail on that one. My old friend, Dr. John Nelson wrote me wondering if I had trouble spelling Brudzinski. We had a good laugh. However, I do try to avoid these mistakes, so if you catch one, please let me know at my e-mail address and I will credit you in the next issue.

Case

A 30-month-old female who has congenital deafness received a cochlear implant with good results (figure 1). Seven weeks later she is seen by her otolaryngologist for evaluation and treatment of some erythema, swelling and drainage around the implant site. This followed being struck by a toy thrown by a sibling a few days earlier. A culture was obtained and she was treated with a second-generation cephalosporin. The problem worsened and the culture grew methicillin-resistant Staphylococcus aureus (MRSA). She was then admitted to the hospital for removal of the implant and treatment with vancomycin (figure 2).

What other complication is associated with cochlear implants?

1. Tinnitus
2. Diplopia
3. Meningitis
4. Echolalia

Answer

The answer is bacterial meningitis (C). The cochlear implant is the real-life bionic ear (figure 3) and has made hearing possible for thousands of deaf children.

However, in July 2002, the FDA notified physicians of the increased possibility of bacterial meningitis after receiving a cochlear implant. The reported incidence is three per 1,000, and two thirds of cases have been younger than 7 years of age. The majority are caused by Streptococcus pneumoniae, but the exact mechanism is unknown. However, it is known that having an inner ear or temporal bone malformation puts the patient at increased risk of bacterial meningitis (figure 4, a postmortem picture of a temporal bone defect resulting in bacterial meningitis complicating otitis media).

Also, a history of labyrinthitis or a past history of meningitis associated with otitis media predisposes the patient to this complication. Therefore, most of these patients undergo special imaging of the temporal bones prior to implantation.

Pediatrician’s role

These are considerations used by the otolaryngologist in the decision-making process, but the pediatrician’s role is to be sure that the candidate for cochlear implant is properly immunized. This includes pneumococcal, meningococcal and Haemophilus influenzae type b vaccines. An excellent, brief review of this problem can be found in The Pediatric Infectious Disease Journal (Bluestone CD. 2003.22(5):477-478.)

This case offers another teaching point. Methicillin-resistant Staphylococcus aureus (MRSA) has become the rule rather than the exception (at least at our hospital). The vast majority of the Staphylococcus aureus isolates recovered in our lab now are methicillin resistant. Empiric anti-staph therapy for serious infections of hospitalized children now must include either vancomycin or clindamycin. Some are starting therapy with clindamycin pending culture and sensitivity results since most community-acquired MRSA (CA-MRSA) are sensitive.

However, if it is an erythromycin-resistant strain of CA-MRSA, one should ask the microbiology lab to perform a D-test, to rule out inducible resistance to clindamycin. Our lab now performs this test automatically. The “D” refers to the shape of the zone of inhibition around the clindamycin disk when placed within about 20 mm from an erythromycin disk (figures 5&6), as opposed to a negative “D” test as shown in figure 7 with a symmetric zone of inhibition around the clindamycin disk. If the “D” test is positive, then inducible resistance to clindamycin is possible, and another drug should be used. Often, trimethoprim-sulfamethoxazole, possibly with rifampin may be used. In older children, minocycline may also be an option. An excellent review of this phenomenon can be found in The Pediatric Infectious Disease Journal (2002. 21:530-534.) Lastly, clindamycin should NEVER be used if the central nervous system (CNS) is (or possibly) involved, as it does not get there.

Our patient had a good outcome, and was scheduled for another implant to be placed on the other side. The otolaryngologists tell us that there can only be one implant per ear. So a patient only gets two shots at this procedure. And, by the way, some patients do complain of tinnitus after the implant is placed. So, technically, answer A is also correct.

Columnist comments: Last year I commented on the First Annual James W. Bass Visiting Professorship, which was sponsored by, and held at The Uniformed Services of the Health Sciences (USUHS), Department of Pediatrics at the F. Edward Hébert School of Medicine in Bethesda, Maryland. While the USUHS will continue to sponsor this annual event, it is to rotate to various Air Force, Navy and Army medical centers around the country. This year it will be held in Hawaii at Tripler Army Medical Center, near Honolulu, Jim Bass’ long-time professional home. It is set for May 19th and 20th. This is primarily a uniformed services event, but anyone can attend. Now before you call your travel agent for tickets, you may want to know that I am to be the visiting professor for this second annual event. On the positive side, it’s free, and with me delivering the lectures, it will be worth every penny. If you are interested in attending, just e-mail me and I’ll provide the details. In the July 2005 issue, I will report on how it went.

On a serious note, I went through my infectious disease fellowship with Jim at Tripler more than 20 years ago. I did not know Dr. Bass when I arrived in 1982, but I left in 1984 with a deep, life-long respect for him and “his” Tripler Army Medical Center. I modeled my career after Jims’ style, and while it’s an admirable goal, it can never be achieved.