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Cerebrospinal Fluid LeaksMichael E. Decherd, MD

Byron J. Bailey, MDMay 26, 1999

IntroductionCerebrospinal fluid (CSF) may pathologically communicate with the outside world. This may becaused by a diverse set of etiologies. Diagnosis and treatment can be challenging and continues to evolve.This manuscript will explore the pathophysiology and management of CSF fistulae.

HistoryCSF rhinorrhea has been described as far bac as the time of !alen ("#). $n the %iddle &ges an

association with head trauma ('). The topic was first reviewed by %iller in "'# ('). Spontaneous CSFotorrhea was first described in "* by a French physician in a "+,year old girl who had had intermittentotorrhea for eighteen months and a fistulous opening in roof of the inner third of her ear canal. -ithcautery the otorrhea ceased (*). Dandy first described an intracranial repair of a CSF lea in "'# andDohlman in "/ was the first to describe the extracranial repair which he did via a naso,orbital incisionfor an anterior cranial fossa CSF lea. 0irsch and later 1rabec described trans,nasal approaches and-igand in "" was the first to describe the use of endoscopes in the repair of small leas incurred during

ethmoidectomy (""). The last twenty years has seen a refinement in the techni2ues and materials used forendoscopic repair of CSF leas and encephaloceles.

Basic ScienceCerebrospinal fluid is manufactured mostly in the choroid plexus in the lateral ventricles. $t then

traverses the third and fourth ventricles where it egresses into the subarachnoid space via the foramina of3uscha and %agendie. $t circulates throughout the meninges between the arachnoid and the pia and

provides a layer of protection for the neural tissue. $t is reabsorbed by the venous system via arachnoidvilli which pro4ect into the venous sinuses (5) .

The composition of CSF is similar to that of serum with some minor differences. %oreimportantly as an ultrafiltrate of serum abnormalities of serum values (hyperglycemia for example) will

be reflected in the CSF given enough time for e2uilibrium to be reached. &dults average "/+ m3 of CSFvolume and the pressure of CSF under normal conditions can range between 6+ and "+ mm0'7. &new body regenerates its CSF volume three times per day.

8eta,',tranferrin is a protein which is only found in CSF perilymph and vitreous humor (6). $tdeserves special mention as an important marer when one is trying to determine the etiology of nasaldischarge as it generally indicates a CSF lea.

Classification&s the study of CSF leas has progressed the literature has not had a consensus regarding the

terminology used to describe them. & recent editorial by 0ar,9l summari:ed here may resolve some ofthe confusion.

CSF leas may be traumatic or non,traumatic. Traumatic leas may be surgical or non,surgicaland surgical leas may be planned (e.g. failed reconstruction) or unplanned while non,surgical leas may

be penetrating or non,penetrating. &ll of the above may be subclassified as either immediate or delayed.;on,traumatic leas may be subdivided as high pressure or normal pressure leas. 0igh pressure

leas may be due to tumors hydrocephalus or benign intracranial hypertension. ;ormal pressure leas

may be due to a variety of reasons including congenital defects tumors arachnoid granulationsinfection empty sella and idiopathic causes ()

&n older scheme which persists in the literature includes the one devised by 7 leas which were idiopathic in origin and=secondary spontaneous> leas in which a cause was identified. 7mmaya preferred avoiding the use ofthe term =primary spontaneous> as a wastebaset classification for which a cause has not been discoveredand advocated avoidance of the use of =secondary spontaneous> as a logistically impossible phrase. 0ar,9l notes that many of the =spontaneous> leas are probably delayed,onset non,surgical traumatic leasand avoids the term =spontaneous> altogether reserving =idiopathic> for cases in which no cause can be

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identified. ;evertheless the term =spontaneous> persists in the literature and in practice to refer to leaswhich appear without a clear antecedent trauma.

&nother important designation when evaluating a CSF lea is that of high,flow or low,flow. &high,flow lea can be actively seen. & low,flow lea cannot but its presence is highly suspected clinically(for example a post,op F9SS patient with unexplained pneumocephalus). $n general a low,flow lea ismore difficult to diagnose but responds better to more conservative measures whereas in a high,flow leathe converse is true.

Epidemiology&pproximately +? of CSF fistulae with resultant rhinorrhea are caused by non,surgical trauma

"#? by surgical trauma with only 5,/? having a non,traumatic cause ('). CSF fistulae have been foundto occur in 5? of closed head in4uries ? of penetrating head in4uries and "+? to 5+? of basilar sullfractures ("'). Traumatic fistulae are most common in males in the third to fifth decades. 9ighty percentwill present in the first / hours and 6? will present by three months ("#). %eningitis occurs in

between "+? and '6? of head trauma cases with a CSF lea (#) has a mortality of approximately "+?("'). Series from the first half of the century indicate that two,thirds of post,traumatic CSF leas willresolve spontaneously by one month ("). @ost,traumatic leas are +? cranio,nasal and '+? cranio,aural with the latter having a better chance of spontaneous closure (").

&s far as otologic issues related to CSF leas spontaneous CSF otorrhea is rare and usuallypresents in childhood with symptoms referable to labyrinthine malformations (such as a %ondini

deformity) or meningitis (*). $n one series the median age of presentation was four years with '?presenting with recurrent pnemococcal meningitis and #? with an associated unilateral or bilateralsensorineural hearing loss ("6). %ost cases of CSF otorrhea follow trauma and the second,most commoncause is post,surgical. &fter trans,labyrinthine acoustic tumor surgery a large series from the 0ouse 9arClinic showed an incidence of CSF leas of #.? and found that it was unrelated to patient age tumorsi:e or operative time. %eningitis occurred '.? of the time and was only related to larger tumors ("/).

DiagnosisAnless identified at time of surgery diagnosing a cerebrospinal fluid fistula can be difficult. &

high index of suspicion must be present in patients with unilateral rhinorrhea. 7f note rhinorrhea maybe a sign of a fistula of aural origin via the eustachian tube. & thorough history may reveal an antecedenthistory of trauma or meningitis. Depending on the clinical picture the physician has a variety of differenttests he or she may employ.

The simplest tests are easy to perform but not very accurate. The halo sign is present when nasal

secretions on bed linens or dressings form a halo. This occurs when CSF mixed with blood spreads ontoan absorbent surface. The darer blood chromatographically forms a ring around a lightly,stained centerforming a halo (6). %ixture of blood with tears or saliva can give false,positives.

&nother simple test involves collecting rhinorrhea on a handerchief. ;asal secretions will dryand leave a stiff residue whereas CSF will dry and leave the cloth soft.

The laboratory plays a ey role in the diagnosis of CSF rhinorrhea. 7ne of the more simplethings for which to chec is glucose. ;ormally nasal secretions are devoid of glucose whereas CSF has aglucose level related to the plasma glucose. The literature generally supports a glucose value of 5+ mgBd3in rhinorrhea fluid as indicative of CSF. 0owever there are opportunities for false,positives and false,negatives. For example a post,surgical patient may have a serous exudate which physiologically containsglucose. Conversely a patient with an advanced meningitis may have a decrease in his or her CSFglucose (see Table ").

The gold standard for laboratory diagnosis of CSF fistulae is beta,',transferrin. This protein isfound in only three bodily fluids CSF perilymph and vitreous humor (6). Therefore unless a patient

has an open globe ongoing production of clear nasal discharge that is positive for beta,',transferrin ishighly diagnostic for CSF. &t our institution the lab re2uires " m3 of nasal or oral secretions and an SSTtube of blood (gold,topped tube). esults are reported in four days.

&t times collection of rhinorrhea can be a problem. $n a comatose patient one can turn thepatient onto his or her side and try and collect fluid or in an alert patient one can have the patient1alsalva to try and increase flow. &dditionally one may collect fluid and elicit a physical exam findingwhen checing for the reservoir sign in this the patient is supine for a length of time and then broughtinto an upright position with the nec flexed. & rush of clear fluid is a sign of a fistula. $f these measuresare unsuccessful one must turn to alternate means of diagnosis.

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undesirable the decision to delay the surgical treatment of a potential CSF fistula until after treatment offacial fractures is a defensible one as the fracture reduction aids healing of dural tears (#"').

@ostoperative care includes many of the measures discussed before. &voidance of snee:ing andcoughing use of laxatives to avoid straining at stool elevation of the head of bed and bedrest areimportant to give the grafts time to heal. 7ther measures such as the use of a lumbar drain and antibioticsare controversial.

Controversies7ne controversy regards the use of prophylactic antibiotics. $f a CSF lea is diagnosed should

one treat empirically to avoid meningitisE @roponents argue that meningitis is bad enough to warrant theuse of prophylactic antibiotics despite no data which show their efficacy. 7pponents feel that they areineffective and lead to coloni:ation by more serious flora. 7ne author who recently reviewed the literatureconcluded =The use of prophylactic antibiotics is neither recommended or condemned by evidence ofefficacy. 0owever their use is cautioned against by evidence of a subse2uent change in nasopharyngealflora to potentially more invasive organisms> ("5).

&nother controversy that arises is the benefits of intracranial repair versus extracranial repair.&dvantages of an intracranial approach include direct visuali:ation the ability to repair ad4acent cortexand a better chance of repairing a lea caused by increased intracranial pressure. The disadvantagesinclude increased morbidity longer hospitali:ation and higher incidence of post,operative anosmia. 7nthe other hand and extracranial repair has decreased morbidity and anosmia as well as superior exposure

of the posterior ethmoid parasellar and sphenoid regions. 0owever it is less suited for defects in thefrontal sinuses with prominent lateral extension and is less successful in high,pressure leas ("#).&lthough the literature generally shows a higher successful rate of repair with extracranial approaches inthe end the choice of approach depends on the experience of the surgeon and the particular details of thecase at hand (""+"").

7ther treatment decisions exist in which clinicians do not have the benefit of scientific studies toguide them and these decisions usually fall to the experience of the surgeon and the clinical scenario.9xamples of these include the use of a lumbar drain post,operatively the length of time to try conservativemeasures before proceeding with surgery and the best materials and approaches with which to closedefects.

Complications%eningitis refers to the inflammation of the meninges and this is a possible se2uela of a CSF

fistula and can occur post,operatively as well. Traumatically,ac2uired meningitis occurs in between "+?

and '6? of cases (#) has a mortality of approximately "+? ("'). The pathogen depends on thepresentation and is summari:ed in Table ". The patient will feel sic and may have a stiff necphotophobia headache fever mental status changes and Gernig

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