耳蝸植入與細菌性腦膜炎之間可能有關係

Gov't正在尋找其他未報導病例的資訊

  耳蝸植入會增加細菌性腦膜炎的發生危險嗎?還是說,導致這種疾病危險增高的是耳聾相關的因素,與患者是否進行植入沒有關係?這是美國疾病控制中心(Centers for Disease Control and Prevention,CDC),美國食品藥品管理局(the Food and Drug Administration,FDA),進行這項手術的耳鼻喉科醫師,植入物的生產廠家以及植入者和他們的家庭,所共同面對的問題。FDA估計,全世界已經進行了6萬多例這種手術,耳蝸植入可以點啟動內耳中的聽神經纖維,從而恢復耳聾者的聽力。

  問題的程度

  亞特蘭大CDC國立感染性疾病中心的醫學流行病學家Cynthia G. Whitney醫師MPH說,接受耳蝸植入者,發生細菌性腦膜炎的危險要比一般人高。FDA收到植入者中細菌性腦膜炎的發生率比預期要高的報告後,就發出了一封信,指出這種設備與細菌性腦膜炎,特別是肺炎球菌性的腦膜炎的發生,可能存在關聯。FDA在7月24日說,全世界共報告有25人發生腦膜炎,其中7人死亡。其中有兩例死亡,發生在美國,其他發生在歐洲。FDA在這封信中說,對進行此項手術的醫療中心進行的初步研究,顯示在耳蝸植入人群中,有其他的未報導的腦膜炎病例。

  美國密爾沃基市威斯康辛醫科大學耳鼻喉科與交流科學系教授兼主任Phillip A. Wackym醫師說:現在還不清楚,這個問題究竟有多嚴重。他是一個對所有三家廠商的設備進行過研究的大型耳蝸植入專案的醫學負責人。Wackym說:採用Cochlear有限公司與the Advanced Bionics公司的裝置的患者,發生了腦膜炎。儘管另外一家植入裝置的生產廠家,Med-El有限公司聲稱,全世界採用他們的植入裝置之一的患者,他們還不知道有一例患者發生腦膜炎。

  但Wackym說,他認為,這可能是由於醫師們的漏報有關,或者採用Med-El公司的裝置進行的植入數目不夠大,在5歲以下的兒童中,每年發病率大約7例/100,000人,2歲以下兒童中,每年發病率20例/100,000人的情況下,無法檢測到腦膜炎的病例。

  Wackym說,北美的植入者發生的兩例腦膜炎導致的死亡,都是採用Advanced Bionics有限公司的裝置的兒童。到現在為止,在美國,接受Cochlear有限公司的植入裝置(Nucleus裝置)的各年齡組的患者(共 15,000例植入)中,有14人發生腦膜炎,而接受有限公司的植入裝置(Clarion裝置)的患者(共7,000例植入)中,有8例發生腦膜炎。

  芝加哥兒童記憶醫學中心聽力學的醫學主任,、耳科學/神經科學負責人Nancy M. Young醫師對300多位兒童進行了植入,到現在為止,她只知道她所進行植入的孩子中,只有一人發生肺炎球菌性腦膜炎。她說:我跟在其他大的醫學中心的同事談過,而且腦膜炎並不是那麼常見,這不是流行。

  不過,Young說她相信,有一些病例沒有被發現,或者沒有報告。實際上,對她自己的患者,她剛開始的時候,也沒有意識到,腦膜炎與植入有關係。只是在其中一家廠商,Advanced Bionics提出這個問題之後,在植入者腦膜炎的發生率比預期要高得到報道之後,這個問題才引起她的注意。

  現在正在進行腦膜炎病例的調查, Young說人們認為,存在病例的漏報,因為腦膜炎是在手術後數周乃至數月後發生的。目前還不清楚,腦膜炎的發生,是否與植入有關係。

  耳聾的病因

  美國每1,000位兒童中,就有一位有嚴重或者完全的聽力損失。兒童耳聾的主要原因包括(按照頻率排列)中耳炎的併發症,先天性障礙以及其他獲得性的聽力損失,例如腦膜炎以及其他感染,使用耳毒性藥物以及腦震蕩等。Wackym說,北美接受耳蝸植入的5,000位少兒中,有500人人在進行手術之前,就發生過腦膜炎。

  Young說,腦膜炎曾經是中耳炎之外,最常見的獲得性耳聾的病因,不過在七價滅活肺炎球菌疫苗(Prevnar)廣泛應用後,其出現了引人注目的下降,這種疫苗對於2歲以下的幼兒有效(年齡很小的兒童,其免疫系統對於23-價肺炎球菌多糖疫苗反應不強烈。)

  植入與腦膜炎

  有些人耳聾是因為他們的耳蝸生來就是異常的,這使他們發生腦膜炎的危險增加,Whitney說:而且有些人是由於腦膜炎而患耳聾的,這就意味著,他們發生第二次腦膜炎的危險比較高。

  Young不太同意那些已經發生了一次腦膜炎的人,再發生這種疾病的危險會增高的觀點。耳蝸畸形與腦膜炎的危險存在關聯,不過,這通常與腦脊液(CSF,cerebrospinal fluid)泄漏有關。腦膜炎自身並不意味著疾病復發的危險會升高,除非存在著CSF,但這並不常見。Wackym說,他相信,接受植入者腦膜炎發病危險的增高,有部分解剖學與手術上的原因。把電極置入耳蝸的過程中,內耳(鼓室階)打開直接與中耳相通。放置電極後,繃帶,顱骨膜或者肌肉放在電極周圍,以封閉開口(也就是cochleostomy)。在治療早期,如果發生中耳炎的話,那麼沒有機械障礙能夠阻止微生物進入耳蝸,然後進入CSF。

  Wackym說,兒童是受腦膜炎影響最大的人群。術後早期病例,非常可能會有隱藏著細菌的生物薄膜,這些細菌繁殖擴散,可以導致急性中耳炎。晚期病例非常有可能會在cochleostomy時,存在不完全的屏障。這可能是由於手術的問題(cochleostomy的封閉不全或者封閉失敗-),電極部分遷移出cochleostomy,或者用於封閉cochleostomy的組織的萎縮。

  腦膜炎與疫苗

  全世界最初向FDA報告的25個病例中,有5個人有疫苗使用史,這些人中,沒有人接受任何一種肺炎疫苗。看起來,接受植入者有很多因素在不理想的免疫率中起作用。

  首先,研究者們不認為耳蝸植入手術可以增加腦膜炎的危險,Young說,乳突手術並不會增加腦膜炎的危險,不接觸CSF的頭部手術與頸部手術,也不會增加其危險。(相反,腦積水腦室動靜脈吻合術直接接觸CSF,其與腦膜炎以及其他CNS感染危險增高之間的關聯,很久以前,就被人們認識到。Young想知道,其他的植入,例如帕金森氏症的神經外科植入手術,是否也會增加腦膜炎的危險。)因此,疫苗預防並沒有包括在手術程式之中,而是被當作患者的初級保健醫師的責任。

  Wackym 說:說實話,這不是我們讓彼此做的事情。 Young也說:外科醫師不是按照初級保健醫師訓練的。另外,在2000年2月,Prevnar批准應用之前,還沒有有效的給兩歲以下兒童使用的疫苗。幾乎在此之前出生的所有兒童,在他們生命最重要的最初幾年中,都沒有肺炎球菌疫苗可供選擇。當然,多糖疫苗已經出現很多年了,可以有效地減少侵入性的肺炎球菌性疾病,包括腦膜炎在內,適用於兩歲以上個年齡組的人。

  最近,Prevnar出現短缺,這種短缺要比預期的時間更長,也更嚴重,這使免疫實踐諮詢委員會(Advisory Committee on Immunization Practices,ACIP)修訂了他們的肺炎球菌接種指南。不過,這些修正並沒有改變原來對5歲以下,發生侵入性肺炎球菌性疾病高危的兒童,進行接種的建議,這部分高危兒童包括所有2歲以下的兒童以及2-4歲,患有CSF泄漏或者其他某些特定的醫學狀況的兒童。由於這些病例得到報道,因此研究者認為,接受耳蝸植入者,包括屬於高危險群。

  奧古斯塔市喬治亞醫科大學內科學教授David R. Haburchak醫師對為什麼這些兒童中有些人沒有接受肺炎球菌疫苗接種作出了更系統的解釋。我相信,這個國家有危險的個體中,疫苗沒有得到充分的應用的主要原因,是由於缺少可以促進患者與臨床醫師干預的持續追蹤與記錄系統,就象IRS或者每年煙霧水平證明那樣。

  他認為:在我們進行全民保險,將其與全民初級保健資料收集與監測系統聯繫起來之前,不可能為這種或者其他任何一種衛生措施提供足夠的初級保健。

  去年九月份的《Annals of Internal Medicine》雜誌上發表的一篇文章中,Emory大學的Phillips及其同事提出臨床惰性這一名詞,他們用這個名詞來描述衛生保健提供者,能在需要的時侯提供或者加強治療,特別是在這種治療其作用是保持健康,不是緩解症狀時,更是如此。自從好撒瑪利亞人的那個比喻開始,醫學的做法就是援救,Haburchak說:要完全實行有益的預防措施,需要醫學觀點以及醫療實踐的重大轉變。

  改變接種策略

  然而,細菌性腦膜炎的病例,是給那些與接受植入者打交道的醫師的一個警鐘。現在,這個問題正在引起對耳蝸植入醫師的群體教育,我們現在給所有的接受耳蝸植入的患者進行免疫接種。

  Young也說,她認為接種對於保護患者而言,是非常重要的。在我們得到更多資訊之前,她說:我們假設接受耳蝸者,發生腦膜炎的危險會有輕微的增高是適宜的。因此,為什麼不給他們接種肺炎球菌疫苗呢?她給她所有的病人寫了一封信,推薦他們通過他們的初級保健提供者,進行肺炎球菌接種。如果他們獲取這種疫苗有困難的話,她的門診部會給他們安排。

  另外,Young說她相信,給大學年齡的耳蝸植入者,接種腦膜炎球菌疫苗也是明智的,因為即使是某些健康的青少年以及青年人,也會有發生這種疾病的危險。她在給她的耳蝸植入病人的初級保健醫師的一封信中,推薦給他們接種各年齡段適宜的疫苗。她說:疫苗有如此大的意義。難道只因為沒有觀察到腦膜炎球菌的病例,就意味著沒有危險嗎?

  另外,她說她認為年紀較大的接受植入者,不應該被遺漏。也應該給老年人接種肺炎球菌疫苗,她說:他們是接受耳蝸植入增加最快的人群。她說侵入性肺炎球菌性疾病,包括腦膜炎呈U型曲線。我們在考慮兒童的問題的同時,也開始考慮老年人的問題了。

  疫苗可以降低腦膜炎的發病率

  FDA說,即將接受耳蝸植入者以及已經植入者,接種通常導致細菌性腦膜炎的病原體疫苗,特別是肺炎球菌與嗜血流感桿菌疫苗,可能會有好處並且應該弄清楚所有人的免疫狀態。FDA推薦,應該根據當前的ACIP指南,進行疫苗的選擇。

  推薦對所有2歲以下幼兒以及2至4歲,患有慢性疾病的兒童,接種肺炎球菌滅活疫苗(Prevnar) Whitney說:推薦給所有65歲及以上的人以及2至64歲,患有某些慢性疾病的人,接種肺炎球菌多糖疫苗(Pneumovax),因此2至4歲,患有慢性疾病的兒童,應該接種兩種疫苗。FDA的聲明是合理的,對這些建議,也提供了支援。Wackym還說:為給非常小的幼兒接

Possible Link Between Cochlear Implants and Bacterial Meningitis

Gov't Seeks Information on Additional Unreported Cases

By Harry Goldhagen
WebMD Medical News

Reviewed by Gary D. Vogin, MD

Aug. 5, 2002 -- Do cochlear implants increase the risk of bacterial meningitis? Or do the factors associated with deafness predispose to this disease, regardless of whether the patient has received an implant? That is the question facing the Centers for Disease Control and Prevention (CDC), the Food and Drug Administration (FDA), otolaryngologists who perform this procedure, manufacturers of the implants, and implant recipients and their families.

The FDA estimates that more than 60,000 such procedures have been performed worldwide. Cochlear implants electrically activate auditory fibers in the inner ear to restore hearing to deaf individuals.

Extent of the Problem

What is clear is that cochlear implant recipients are at higher risk of bacterial meningitis than the general population, according to Cynthia G. Whitney, MD, MPH, medical epidemiologist with the National Center for Infectious Diseases (NCID) at the CDC in Atlanta. After receiving reports of higher than expected rates of bacterial meningitis in implant recipients, the FDA issued a letter about a possible association between this device and the development of bacterial meningitis, specifically pneumococcal meningitis. Worldwide, 25 cases and nine deaths have been reported as of July 24, according to the FDA. Two deaths occurred in the U.S. and the others in Europe. Preliminary surveys of centers performing this procedure "suggest there are additional, unreported cases of meningitis in the cochlear implant population," according to the FDA letter.

"It's not clear yet how big the problem is," says Phillip A. Wackym, MD, professor and chairman of the department of otolaryngology and communication sciences at the Medical College of Wisconsin in Milwaukee. He is medical director of a large cochlear implant program that has studied devices from all three manufacturers.

"Patients with the Cochlear Corp.'s and the Advanced Bionics devices have developed meningitis," Wackym says. Although another maker of the implants, the Med-El Corp., has claimed it knows of no cases of meningitis in any patient worldwide who has received one of its implants, Wackym says he thinks this may represent underreporting by surgeons, or the number of implants performed with the Med-El devices may not be high enough to detect pneumococcal meningitis cases above the annual background rate of around seven per 100,000 in children younger than five years, or 20 per 100,000 in those younger than two years.

According to Wackym, the two meningitis-related deaths among implant recipients in North America were both children with Advanced Bionics Corp. devices. So far, there have been 14 cases of meningitis (of 15,000 implants) among all age groups in the U.S. who received a Cochlear Corp. implant (the Nucleus devices) and eight cases (of 7,000 implants) who received an Advanced Bionics Corp. implant (the Clarion devices).

Nancy M. Young, MD, head of the Otology/Neurotology Section and medical director of audiology at Children's Memorial Medical Center in Chicago, has performed more than 300 implants in children, and yet she knows of only one child from her clinic who developed pneumococcal meningitis. "I've spoken to my colleagues at other large centers, and meningitis has not been seen much. It's not an epidemic," she says.

However, Young says she believes that some cases may not have been recognized or reported. In fact, with her own patient, she did not at first realize that the meningitis may have been related to the implant. It was only after one of the manufacturers, Advanced Bionics, raised the issue, after reports of higher than expected rates of meningitis in implant recipients, and brought it to her attention.

"There is a survey for meningitis cases under way now," Young says. "It's thought that there has been underreporting of cases, since they have occurred weeks or months after surgery, and it has not been clear they've been related to the implant."

Causes of Deafness

About 1 of every 1,000 children in the U.S. has severe or profound hearing loss. The main causes of deafness in children are (in order of frequency) complications from otitis media, congenital disorders, and other acquired causes of hearing loss, such as meningitis and other infections, ototoxic drugs, and head trauma. According to Wackym, 500 of the 5,000 young children in North America who received cochlear implants had meningitis before undergoing this procedure.

Meningitis used to be the most common reason for acquired deafness after otitis media, Young says, but this has dropped dramatically since the widespread use of the seven-valent conjugate pneumococcal vaccine (Prevnar), which is effective in children younger than 2 years. (The immune system of very young children does not respond strongly to the 23-valent pneumococcal polysaccharide vaccine [Pneumovax].)

Implants and Meningitis

"Some people are deaf because they are born with cochlear abnormalities, which may lead to a higher risk of meningitis," says Whitney. "And some people may become deaf from meningitis, which means they are more at risk for a second episode of meningitis."

Young qualifies the notion of an increased risk of meningitis among those who have already had one instance of the disease. "Cochlear malformation is associated with a higher risk for meningitis, but this is generally related to a CSF [cerebrospinal fluid] leak. Meningitis itself doesn't mean an increased risk for recurrent disease unless there is a CSF leak, which is unusual."

Wackym says he believes there are a number of anatomical and surgical reasons for an increased risk of meningitis in implant recipients. "In placing the electrode into the cochlea, the inner ear (scala tympani) is directly opened into the middle ear. After placement of the electrode, fascia, pericranium, or muscle is placed around the electrode array to seal the

    
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