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Oral Medicine
Brain abscess and dentistry: A review ofthe literatnreNorman J,
Schuman '̂ / James E, Turner**
Brain ab.-.cess is a rare, extremely aggressive,
life-threatening infection. A mortality rate ofbe-t^veen 36% and
90% has been reported as recently as 1990. It is resistant to
antibiotics and isone of the few bacterial infections whose
morbidity md mortality statistics remain unaffectedh tf^e
development of antimicrobial medications. Successfid treatment
appears to be depen-dent on early diagnosis, surgical intervention,
and direct antibiotic irrigation ofthe surgicalwound site, as well
as intravenous administration of high doses of antibiotics
throughout thecrisis. It has been .'iuggested that there is a
relationship between dental infection or treatmentand brain
abscess. Dental infection and treatment have been found culpable in
numerouscases reported in the literature. However, careful review
ofthe articles reveals that dental in-fection or treatment has
often been named as a causative factor (1) solely because an
infectionor treatment occurred within several months of brain
abscess: (2) when nondental bacteriawere cultured from the brain
abscess: and (3) without culturing both the dental infection andthe
brain abscess to ascertainßora match. (Qninlessenct Inl 1994:25:41
I^L^.)
Introduction
The practice of dentistry involves the maintenance
andestablishment of good patient oral health by dentalhealth
personnel, including the diagnosis and treat-ment of oral infection
by the dentist. The overwhel-ming majority of infected teeth are
treated conserva-tively by the practitioner, with knowledge that
the like-hhood that dental infection will spread to other areas
ofthe hody is extremely remote. However, some risk doesexist for
the spread of infection even for clinicallyhealthy patients,'
Dental procedures as benign as oralprophylaxis have been reported
to canse infective en-docarditis, brain abscess, and other life-
and health-threatening conditions,'"' Infected teeth have
alsocaused the above-mentioned conditions, in addition toLudwig's
angina and mediastinitis,^'' Untreated dental
Associate Professor, Departmenl of Biologic and
DiagnosticSciences, University of Tennessee, College of
Dentistry,875 Union Avenue. Memphis. Tennessee 38t 63,Professor and
Chairman. Department of Biologic and Diagnos-tic Sciences,
University of Tennessee,
infections are occasionally cited as a cause of serioussystemic
illness and even death by state and federalhealth authorities.^
Infection from dental abscess canspread by either anatomic or
hematogenous routes.The heart, brain, and respiratory system arc at
greatrisk when a dental infection spreads beyond the oralcavity,̂
This paper will foeus on brain abscess and itsrelationship to
dental infection.
Review ofthe literature and discussion
Brain abscess is a rare, life-threatening infection. It hasan
incidence of 1 per ltJIJ.OOO population and has beenreported to be
fatal in 36% to 90% of cases.^"" Reportsof brain abscess associated
with dental infection havestated that most infections reach the
brain via direct ex-tension or cavernous sinus thrombosis, although
bothhematogenous and anatomic routes of infection aresuspected,^'"
Kemper and Aseltine'" argued that ana-tomic extension must be rare
because of the brain'snatural barriers, the skull and dura. They
stated that itis clear, however, that some cases of brain
abscessspread directly from the jaws to the brain anatomicallyby
dissection through fascial spaces.'" All case reports
Quintessence International Volume 25, Number 6/1994 411
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have noted that diagnosis was made through sympto-matic illness.
Symptoms of intracranial abscess are in-dicative of central nervous
system disorder and includemalaise, hyperirritability, lethargy,
confusion, and neu-ropathy (eg, seizures),'-
Brewer et al'-' noted that, of 60 reviewed cases ofbrain
absee,ss, four were attributed to '"dental proce-dure or abscess."
The greatest number of cases (12) wasattributed to "otic or
paranasal sinus infection," Alsoexceeding dental infection as a
cause of brain abscesswere "pulmonary infection" (eight), "general
surgery"(six), "head injury" (five), and "congenital heart
dis-ease" (five). Fifteen of the 60 cases were ot unknownorigin,'"'
Haymaker''' attributed 2S fatal central ner-vous system infections
to odontogenic origin and drewa relationship between tooth
extraction and fatal brainabscess. Tooth extraction appears to be
tbe most com-mon dental factor in patients who are diagnosed
withbrain abscess,'"* Other dental procedures that havebeen noted
include operative dentistry, periodontaltherapy, injection of local
anesthetie, and dental pro-phylaxis,'" '̂̂ '"Gold'-^ reported a
fatal brain abscess in apatient who exhibited dental infection and
was nottreated. He strenuously argued that treatment couldpossibly
have saved the life of this patient,'"
Arch location of the dental infection has little bear-ing on
occurrence of brain abscess. Haymaker'"* attrib-uted incidence
primarily to molars, but maxillary andmandibular teeth contributed
equally to fatal cranialinfection in this study. This finding is
unremarkable,since both hématologie and anatomic spread have
beenreported as possible routes of infection, Andrews andFarnham'
citedHollinetal" as linking dental treatmentto one of five
intracranial infections studied. Only fivecases were studied by
Hollin et al,''
The microbiologie flora found in brain abscesseshave been
varied. Most infections attributed to odon-togenic origin have
noted Streptococcus viridans as theprimary microbe found on
culture.'""•''•^"'̂ However,Brewer et al'' found Streptococcus spp
in 32 of 60 cases,and S viridans in 18 of those 60 cases, but
attributedonly four cases to odontogenic origin.'^ On the
otherextreme, Escherichia coli has been cultured from non-fatal and
fatal brain abscesses attributed to dental in-fection.'""
Periodontal infections contain a wide variety of
an-aerobes,'^'*' Cultures of brain abscesses attributed
toperiodontal origin have Tevealed Peptostreptococcusspecies,
Fusobacterium nucleatum, Staphylococcus epi-dermidis,
Propionibacterium species, Bacteroides spe-cies. S viridans, S
tnitior. S milleri. S sctnguis. and S mu-
tatis. '" '" Marks et al̂ argued that when a brain abscessarises
from a contiguous source, such as the ear or nasalsinus, the
bacterial flora are likely to be representativeof the upper
respiratory tract and arc also likely to hemixed. Respiratory tract
flora are also found in the oralcavity,'̂ Other bacteria attributed
to the oral flora in-clude Staphylococcus aureus, Micrococcus
foetidus,and Ilaemophilusparainfluenzae.^^'-"
Hollin et al'' attributed one of the five intraeranial ab-scess
cases they studied to dental origin. They madethis conclusion on
the basis of a negative culture (ster-ile brain abscess), solely
because the patient had 14teeth extracted between 4 months and 1
month prior tohospital admission. The final extraction was
performed1 month prior to the onset of symptoms, Tlie culturewas
negative, yet, incredibly, the brain abscess was at-tributed to
dental extraction. In a second case attrib-uted to dental
treatment, S viridans and Hparainfiuen-zae were cultured bacteria.^
Haemophilus spp are re-spiratory tract microbes, and their alleged
associationwith dental treatment (in this case the restoration of
apremolar 5 days preadmission) seems less than conclu-sive,'''
Lewis et al"" found the microbial flora in the ma-jority of dental
infections to be mixed, consisting of75% anaerobes. The most common
oral microbes werePeptococcus spp, Bacteroides spp, and S
mitleri.-"
Dental procedures alleged to cause brain abscess in-clude simple
operative dentistry, oral prophylaxis, andthe routine injection of
local anesthetic, Hollin et al'stated that, although the role of
local anesthesia is con-troversial, "a variety of bacteria,
actually or potentiallypathogenic is always present on the oral
mucosathrough which the local anesthetic must be injected. Itis
conceivable that, in a susceptible patient, enoughbacteria may be
transported into the bloodstream tometastasize to a distant area,
such as the brain," Hollinet al'' also cited the work of Round et
al,-' who pro-posed general anesthesia for all dental
procedures,"since their experiments indicated that the injectionof
local anesthetic agents forces bacteria deep intotissues,"
The American Heart Association's"^' guidelines forendocarditis
specifically exempt injection of localanesthetic from mandatory
antibiotic prophylaxis forat-risk patients. Also to be considered
are the millionsof local anesthetic injections administered without
sideeffects,
Tliroughout the literature, there is no example orprofile of the
patient at risk for brain or intracranial ab-scess. There are no
reports of increased incidence ofbrain abscess in patients who have
a history of brain
412 Quintessence International Volume 25, Number 6/1994
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Oral Medicino
disease, encephalitis, meningitis, or head trauma (sub-dural
hematoma, etc). In fact, there is no pattern of epi-demiologie
distribution of reported cases. Brain abs-cess has been
demonstrated to occur without regard toage, race, or gender. One
article stated that one groupat apparently higher risk is medically
compromised pa-tients, such as those with a history of
endocarditis,"Presumably, these patients would be given
appropriateantibiotic prophylaxis by the dentist because of
Iheirat-risk status for endocarditis.
Another troubling aspect of brain abscess is its highmortality
rate. The antibiotic era has had a remarkableeffect on endocarditis
and Ludwig's angina, loweringthe mortality rate to below 10%.'*-
'--•'•' Brain abscess,however, rematns remarkably resistant to
antibiotictherapy, maintaining a mortality rate of 36% to
65%,according to Brewer et al.'' who stated that the lack
ofimprovement tn mortality rates from 195^ to 1973
was-disconcerting,"" Aldous ct al,"̂ in 1987. stated thatthe
mortality rate for brain abscess was 90%. Later ar-ticles have
reported similarly high mortality rates.'"
Summary
Brain abscess, a rare infection with an incidence of 1per
100.000 population, is sometimes linked to dentalinfection or
dental treatment, A review of the medicaland dental literature
demonstrated that a number ofcases that clearly do not appear to be
linked to dentalcauses (Escherichia coli abscess, sterile abscess,
orHaemophilus spp abscess) have been reported as casesof brain
abscess secondary to dental abscess or dentaltreatment. Brain
abscess has a high mortality rate,reportedly between 36% and 90%,
but it can be treatedsuccessfully with a combination of antibiotics
andstirgery.
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