Keywords spontaneous intracranial hypotension - spontaneous cerebrospinal fluid leak - orthostatic
headache - Tc 99m-DTPA
Introduction
Spontaneous intracranial hypotension (SIH) is an infrequent cause of daily persistent
orthostatic headache with an incidence of 5 to 100.000 persons/year.[1 ] Other SIH common symptoms arise from brainstem compression and nearby nerves traction.
Cerebrospinal fluid leaks (CSFL) occur under several conditions: lumbar puncture performed
for contrast myelography, spinal surgery, spinal stab wounds, spine fracture, inadvertent
spinal puncture during epidural anesthesia, traumatic lumbar meningocele, and bronchopleural
subarachnoid fistula due to bronchogenic carcinoma. Nontraumatic leaks result from
cranial base focal areas pathologic destruction such as hydrocephalus, meningocele,
global atrophy, congenital deformities, osteomyelitis or tumors, leading to dura mater
penetration. In very rare cases, no cause can be found and these conditions may be
called spontaneous cerebrospinal leak.[2 ]
Radionuclide cisternography (RNC) can readily demonstrate and has played useful role
in detecting CSFL. Although RNC has been used in many cases, few have been reported
in which CSFL out of the subarachnoid space was detected.[3 ]
Case Report
CFS, a 26-year-old female, presented with one vomiting episode in the last week and
throbbing severe parieto-occipital bilateral orthostatic headache for the last 3 months,
and analgesic daily use. Photo/phonophobia, fever, visual symptoms, vertigo or focal
deficit were absent. No history of comorbidities, trauma, sinusitis, lumbar puncture,
or previous surgeries was found. Patient was normotensive, afebrile, eupneic, without
focal deficits or meningeal irritation signs, Glasgow coma scale was 15, pupils were
isochoric, and Romberg test was negative.
Computed tomography showed bilateral frontoparietal laminar subdural collection. Brain
magnetic resonance imaging (MRI) showed laminar subdural effusion in frontoparietal
lobes with discrete extension to the left temporal region, narrowing cortical sulcus,
inferior brainstem displacement, inferior projection of the cerebellar tonsils toward
the foramen magnum, and signs of venous congestion. Brain MRI showed bilateral frontoparietal
laminar subdural effusion with slight extension to the left temporal region, erased
cortical grooves, inferior brainstem displacement, midbrain located at the dorsum
of the saddle level, and inferior projection of the cerebellar tonsils toward the
foramen magnum without collapse. Spine MRI showed dural sac meningeal thickening with
contrast hypercaptation and epidural venous plexus distension along the spine compatible
with pachymeningeal thickening, without leak localization. Lumbar puncture showed
10 cm H2 O opening CSF pressure.
After receiving 20 mCi of technetium-99m-diethylene-triamine-pentaacetate (99m Tc-DTPA) intrathecally via lumbar puncture, posterior views of the brain and spine
were performed at 0, 1, 2, and 4 hours post-injection. RNC showed bilateral CSFL at
the lower lumbar spine level throughout the study ([Fig. 1 ]) and isotope accumulation was also noted in the kidneys at the 1-hour image ([Fig. 2 ]). Patient's symptoms subsided after conservative treatment (bed resting and hydration)
and she was discharged asymptomatic.
Fig. 1 Technetium-99m-diethylene-triamine-pentaacetate (99mTc-DTPA) radionuclide cisternography
showing bilateral cerebrospinal fluid leak at the lower lumbar spine level throughout
the study.
Fig. 2 Posterior view of technetium-99m-diethylene-triamine-pentaacetate radionuclide cisternography
with isotope accumulation in the kidneys at the 1-hour image.
Discussion
SIH diagnosis is based on clinical history, neurologic examination, neuroimaging studies,
and CSF pressure measurement. SIH is difficult to diagnose and 95% of patients may
initially receive an incorrect diagnosis.[4 ] It is important to understand risk factors and symptoms to obtain appropriate imaging
and avoid care delays. Otherwise, chronic pain and disability ensue with the potential
for more serious neurological sequelae.[5 ]
RNC is used to study the CSF kinetics and for differential diagnosis of hydrocephalus
and surgical shunts patency. The radiopharmaceutical used must follow the CSF flow
without affecting its dynamics and then be reabsorbed quickly into the arachnoid villi.
The chelating agent, DTPA, is ideal for these purposes. DTPA shows no metabolism or
absorption along the ependyma before reaching the arachnoid villi and has low lipid
solubility. RNC is performed by means of injecting 111 In-DTP or 99m Tc-DTPA subarachnoidally. Planar images are acquired immediately and at 1, 2, 4, and
24 hours. Occasionally, 48-hour delayed images are also obtained. Besides offering
a whole spine encompassing view, this prolonged monitoring capability may aid in the
detection of slow or intermittent leaks.
Typically, thoracolumbar spine posterior image taken at 15 to 30 minutes should show
radioactivity cephalad expansion within spinal subarachnoid space. By 1 to 2 hours,
activity should reach basilar cisterns, frontal poles by 2 to 5 hours, sylvian and
interhemispheric fissures by 3 to 5 hours, and over cerebral convexities by 10 to
12 hours. By 24 hours, much of the activity is localized along arachnoid villi in
superior sagittal sinus and less in basilar cisterns. Approximately two-thirds of
the administered radioisotope are cleared via kidneys by 24 hours. Bladder activity
is noted by 9 hours.[6 ]
If there is normal activity over the cerebral convexities at 24 hours, active CSF
leak possibility will be quite slim. Negative findings can save the patient additional
invasive studies and unnecessary radiation exposures. Activity paucity over cerebral
convexities at 24 hours—in the absence of meningitis, subdural hematoma, head injury,
brain surgery history—should point to a strong CSF leak probability.
RNC has been shown to be fairly characteristic in SIH patients, with findings including
parathecal activity, less than 4 hours' renal uptake, and early urinary bladder radionuclide
accumulation, slow ascent along spinal axis, activity delaying, and paucity over cerebral
convexities. If leak is present, isotope concentration at the leak site increases
progressively and isotope passage from basal cisterns to the sylvian fissure and interhemispheric
cistern is reduced, consistent with low CSF pressure state. Direct evidence of spinal
leak was reported in approximately 40% of patients in one series of 67 patients referred
for clinically suspected SIH.[7 ] If SIH is caused by reduced CSF production, then cisternography would probably show
slow isotope egress and high concentration remaining for prolonged period at injection
site.[8 ] Indirect signs are sufficient to establish CSF leakage diagnosis. If RNC does not
show any leak but is suggestive of rapid tracer uptake, presence of generalized CSF
hyperabsorption is not necessarily indicated, but rather, leak presence is below the
study resolution limit. Tracer activity semiquantitative graphical analysis over multiple
craniospinal segments may aid in reduced intracranial activity indirect signs detection
and rapid spinal activity loss and may improve this technique sensitivity and specificity.[9 ]
Several SIH cisternographic findings reports have been published, but lesions that
clearly show the leaking site are rare. The reported case revealed small CSF leak
in the early phase and clearly defined kidney images, which were helpful in lesion
location. RNC is not only the diagnostic investigation key, but is also useful for
better management planning, to help select the patients who need early intervention,
to guide the level of epidural blood patch injection and to evaluate therapeutic effects.
