A cisternogram is a nuclear medicine imaging test that tracks the flow of cerebrospinal fluid (CSF) around your brain and spinal cord. A small amount of radioactive tracer is injected into the spinal canal through a lumbar puncture, and a gamma camera takes images over the following hours to days, showing where the fluid travels and whether something is blocking or leaking it. Doctors order cisternograms primarily to investigate suspected CSF leaks, evaluate a condition called normal pressure hydrocephalus, or check whether a surgically placed shunt is working properly.1Radiographics. Nuclear Cerebrospinal Fluid Imaging: Guide to Procedures and Interpretation The test has been around for decades, and while newer imaging techniques have taken over some of its traditional roles, it still fills specific diagnostic gaps that CT and MRI cannot always cover on their own.
How Cerebrospinal Fluid Normally Moves
Your brain and spinal cord float in cerebrospinal fluid, a clear liquid that cushions, nourishes, and removes waste from the central nervous system. The traditional textbook picture says CSF is produced mainly in structures called the choroid plexuses inside the brain’s ventricles, flows outward into the spaces surrounding the brain and spinal cord, and gets reabsorbed into the bloodstream. More recent research complicates that story, suggesting that CSF production and absorption also happen throughout the brain’s tissue and that CSF movement is not a simple one-way current but more of a local mixing process.2PubMed Central. Evaluation of the Production and Absorption of Cerebrospinal Fluid For practical purposes, what matters for a cisternogram is that the tracer should spread upward from the injection site at the lower spine, move over the surface of the brain, and eventually be absorbed. When it doesn’t follow that expected pattern, the images reveal something useful about what’s going wrong.
Why Doctors Order a Cisternogram
Three clinical situations account for the vast majority of cisternograms. Each one exploits a different feature of the test: its ability to follow CSF flow over time, detect tracer in places it shouldn’t be, or confirm that fluid is (or isn’t) draining through an implanted device.
Detecting CSF Leaks
When CSF escapes through a crack or defect in the skull base, it can drip from the nose (rhinorrhea) or the ear (otorrhea). Pinpointing the exact site of the leak matters because surgery to patch the defect needs a precise target. During a cisternogram for a suspected nasal leak, small cotton pledgets are placed in different regions of the nasal cavity before the tracer is injected. Hours later, each pledget is removed and its radioactivity is measured. A pledget that shows significantly more activity than the patient’s blood serum points to the location of the leak. In one reported case, a pledget placed near the right eustachian tube orifice showed a pledget-to-serum ratio above ten to one, clearly identifying the leak site when the images alone showed only subtle nasal uptake.3PubMed Central. Visual and Quantitative Analysis of Cisternography for the Detection of Cerebrospinal Fluid Leakage
Adding three-dimensional imaging to the cisternogram can improve accuracy further. In one study of patients with confirmed rhinorrhea, SPECT-cisternography after lumbar injection of a radioactive albumin tracer identified the fistula site in seven of eight patients, and surgical exploration confirmed the findings.4PubMed. Detection of rhinorrhoea by cisternography in combination with single photon emission tomography, following lumbar injection of iodine-123-labelled albumin The combination of pledget counts and imaging gives clinicians both a quantitative measure and a visual map.
Evaluating Normal Pressure Hydrocephalus
Normal pressure hydrocephalus (NPH) is a condition in which the brain’s ventricles enlarge even though spinal fluid pressure remains in the normal range. It typically shows up in older adults as a triad of difficulty walking, cognitive decline, and urinary incontinence. The challenge with NPH is that those symptoms overlap heavily with other forms of dementia, especially Alzheimer’s disease. A cisternogram helps by revealing a distinctive pattern: the radioactive tracer refluxes backward into the ventricles and stays there at 24 hours, while failing to flow upward over the brain’s outer surfaces as it should. This has been described as a “heart shape” on front-facing images and a “butterfly” on rear-facing images.5Journal of Nuclear Medicine Technology. 111In-DTPA Cisternography with SPECT/CT for the Evaluation of Normal Pressure Hydrocephalus
That said, a cisternogram can show abnormal CSF dynamics in NPH but cannot by itself predict whether a patient will actually improve after shunt surgery. Other tests, like intracranial pressure monitoring and lumbar infusion tests, share the same limitation.6Dementia & Neuropsychologia. Normal pressure hydrocephalus: Diagnostic and predictive evaluation In practice, the cisternogram is one piece of a larger puzzle that neurologists and neurosurgeons assemble before recommending surgery.
Checking Shunt Function
When NPH or other forms of hydrocephalus are treated with a shunt, a thin tube diverts excess fluid from the brain’s ventricles to the abdominal cavity (ventriculoperitoneal shunt) or from the lumbar spine to the abdomen (lumboperitoneal shunt). These devices can malfunction by becoming blocked, disconnected, or kinked. A radionuclide shuntogram, which is closely related to a cisternogram but involves injecting the tracer directly into the shunt’s reservoir rather than through a lumbar puncture, can show whether fluid is actually flowing through the device. If the tracer reaches the abdomen within the expected timeframe, the shunt is patent. If it pools near the distal end or never appears in the abdomen at all, there’s an obstruction.7PubMed Central. Assessment lumboperitoneal or ventriculoperitoneal shunt patency by radionuclide technique: a review experience cases
The diagnostic accuracy of shuntography appears to be high. One study found an overall sensitivity above 92% and specificity above 96% for detecting shunt malfunction, with no infections or complications attributed to the test itself.8Journal of Neurosurgery. Radionuclide shuntography for cerebrospinal fluid shunt flow evaluation in adults Partial blockages can also be identified: a slow transit of tracer or a focal pooling near the tip of the distal catheter suggests partial rather than complete obstruction.9PubMed Central. Clinical value of radionuclide shuntography by qualitative methods in hydrocephalic adult patients with suspected ventriculoperitoneal shunt malfunction
What Happens During the Procedure
If you’re scheduled for a standard cisternogram (not a shuntogram), here’s roughly what to expect. You’ll be positioned lying on your side or sitting up, and a doctor will clean and numb a small area of your lower back. A thin spinal needle is advanced into the spinal canal at the lumbar level, and a small volume of radioactive tracer is injected into the CSF. The tracer used most often is technetium-99m DTPA, though indium-111 DTPA is another option, especially when imaging needs to continue over a longer period because indium has a longer physical half-life. The injection itself is similar to a standard lumbar puncture and takes only a few minutes.
After the injection, you may be asked to rest flat for a couple of hours, partly to help the tracer begin its journey upward and partly to reduce the risk of a headache from the lumbar puncture. Imaging sessions follow at scheduled intervals. For a CSF leak study, images might be taken at around one, four, and sometimes 24 hours after injection. For an NPH evaluation, the 24-hour images are particularly important because the persistence of tracer in the ventricles at that point is one of the hallmark findings. Each imaging session involves lying still under a gamma camera for about 20 to 30 minutes. If pledgets were placed in the nose for a leak study, they are collected at a specified time, sealed in labeled containers, and taken to the nuclear medicine lab for counting.
Risks and Complications
A cisternogram is generally considered a low-risk procedure, but “low risk” is not zero risk. The complications break into two categories: those related to the lumbar puncture itself and those related to the injected tracer.
The most common complaint after a lumbar puncture is a positional headache, often called a post-lumbar-puncture headache, that worsens when you sit or stand and improves when you lie down. This happens because the needle hole in the membrane covering the spinal cord can continue to leak small amounts of fluid after the procedure. For most people the headache resolves within a few days with rest and fluids. However, in patients who are already being evaluated for a suspected spontaneous CSF leak, the lumbar puncture itself can create a new leak at the puncture site. One study found that half of the patients undergoing cisternography for suspected intracranial hypotension developed MRI evidence of epidural CSF leakage at the puncture site even when a fine 25-gauge pencil point needle was used carefully.10PubMed. Postpuncture CSF leakage: a potential pitfall of radionuclide cisternography A separate study looking at whether needle size affected this outcome found that groups using 22-gauge and 23-gauge needles had a higher but not statistically significant rate of post-lumbar headache.11PubMed Central. Cerebrospinal fluid leakage after radioisotope cisternography is not influenced by needle size at lumbar puncture in patients with intracranial hypotension This is worth knowing if you’re being evaluated for a spontaneous leak: the diagnostic procedure can temporarily worsen the very problem it’s trying to find.
On the tracer side, the radiation dose from a cisternogram is relatively small, comparable to other common nuclear medicine studies. Serious reactions to the tracer itself are rare. There are case reports of aseptic meningitis, a sterile inflammation of the membranes around the brain, occurring after intrathecal injection of various substances including indium-111 DTPA. The available literature suggests that only a small percentage of patients develop clinical symptoms, and the condition resolves on its own.12Elsevier / Clinical Neurology and Neurosurgery. Aseptic meningitis as a complication of scinticysternography utilizing 111indium-DTPA Infection from the puncture itself is a theoretical risk with any lumbar puncture but is very uncommon when sterile technique is observed.
Pitfalls in Interpretation
Even a technically successful cisternogram can produce misleading images if the injection doesn’t go exactly as planned. If the needle tip isn’t properly seated in the subarachnoid space, the tracer can end up in the epidural space instead. The resulting images show an irregular initial pattern and poor diffusion along the normal CSF pathways, which can look alarmingly similar to a severe CSF leak. In reported cases where this happened in patients with chronic symptoms, the epidural injection was only recognized because MRI showed no typical signs of a real leak, prompting a second look at the cisternographic images.13PubMed. Unsuccessful tracer injection in radionuclide cisternography revisited The practical takeaway: if cisternogram results don’t match the rest of the clinical picture, the possibility of a misdirected injection should be considered before concluding that a patient has a dramatic CSF leak.
Another subtlety involves ventricular reflux. Seeing tracer in the ventricles at four hours is actually considered a normal finding; it’s only the persistence of ventricular tracer at 24 hours, combined with absence of flow over the brain’s convexities, that points toward NPH.5Journal of Nuclear Medicine Technology. 111In-DTPA Cisternography with SPECT/CT for the Evaluation of Normal Pressure Hydrocephalus Misreading the four-hour image without waiting for the later study could lead to a false diagnosis.
How a Cisternogram Compares to Other Imaging
A cisternogram is not the only way to look at CSF flow or find leaks. High-resolution CT can detect the bony skull-base defects that allow CSF to escape, and in one comparison it identified bone defects in about 71% of patients with confirmed CSF leaks. Among those patients, roughly two-thirds also had positive results on radionuclide cisternography or CT cisternography. When the patients eventually had surgery, the intraoperative findings matched the high-resolution CT in every case.14PubMed Central. Evaluation of CSF leaks: high-resolution CT compared with contrast-enhanced CT and radionuclide cisternography That suggests CT is very good at finding the structural defect, while cisternography’s added value lies in confirming active leakage and measuring how much fluid is getting through.
MRI-based cisternography, which uses heavily fluid-weighted sequences to produce bright images of CSF spaces without any injection, is also gaining ground. These sequences offer high spatial resolution, three-dimensional capability, and no radiation exposure.15PubMed Central. Imaging review of cerebrospinal fluid leaks Their limitation is that they show anatomy rather than flow dynamics. A bright fluid signal near a skull defect on MRI cisternography suggests a leak site, but it doesn’t prove the fluid is actively moving through it the way a radionuclide cisternogram can.
In the workup for NPH, MRI plays a different and complementary role. Specific measurements of ventricular size and the shape of CSF spaces on MRI can help distinguish NPH from Alzheimer’s disease, which can produce overlapping symptoms. The most distinctive MRI features of NPH include small subarachnoid spaces over the brain’s convexity along with enlarged basal cisterns and Sylvian fissures.16PubMed Central. Comparison of CSF Distribution between Idiopathic Normal Pressure Hydrocephalus and Alzheimer Disease When these anatomical signs are equivocal, a radionuclide cisternogram adds functional information about how CSF is actually moving, which neither CT nor MRI can provide on their own.
Use in Children
Cisternograms are far less common in children, but they do have a role in selected cases. Complex pediatric hydrocephalus can involve multiple cysts within or around the ventricles, and it’s not always clear from standard imaging whether a cyst is communicating with the rest of the CSF spaces or is sealed off. In a preliminary report on gadolinium-enhanced MR cisternography in pediatric patients, the technique helped differentiate isolated ventricles from communicating cysts in all four cases where this was the clinical question. Across the studied group, the imaging findings influenced or changed clinical decisions and surgical planning in eight patients, and no side effects were observed.17PubMed Central. Cisternography and ventriculography gadopentate dimeglumine-enhanced MR imaging in pediatric patients: preliminary report This MR-based approach avoids radiation altogether, which is a meaningful advantage when the patient is a child.
When a Cisternogram Changes the Plan
There’s a practical question behind most diagnostic tests: will the result actually change what the medical team does next? For a cisternogram, the answer depends heavily on the clinical scenario. In a patient with clear watery nasal drainage after head trauma, the pledget cisternogram can provide the definitive proof of a CSF leak that triggers a surgical referral. In a patient with a shunt and worsening headaches whose CT looks ambiguous, a shuntogram showing no tracer reaching the abdomen can move the patient straight to the operating room for shunt revision.
The picture is murkier for NPH. As noted above, the cisternogram can demonstrate abnormal CSF dynamics, but no single test reliably predicts who will walk better or think more clearly after shunt placement.6Dementia & Neuropsychologia. Normal pressure hydrocephalus: Diagnostic and predictive evaluation Many centers have shifted toward using a large-volume lumbar drain trial as the primary predictor of surgical success, reserving the cisternogram for cases where the clinical picture remains uncertain after other tests. The cisternogram hasn’t disappeared from the NPH workup, but its weight in the decision-making process has diminished over the past couple of decades as more emphasis is placed on clinical response to temporary CSF drainage.
For shunt evaluation, the radionuclide approach remains robust. The high sensitivity and specificity reported in the literature give surgeons confidence in acting on the result, and the test itself rarely causes complications.8Journal of Neurosurgery. Radionuclide shuntography for cerebrospinal fluid shunt flow evaluation in adults When you consider that the alternative is often exploratory surgery to physically inspect a shunt, a 30-minute nuclear medicine study that answers the question with over 90% accuracy is a good deal for the patient.
What to Expect Afterward
Recovery from a cisternogram is largely recovery from the lumbar puncture. Most centers recommend lying flat for at least a couple of hours post-injection, then gradually resuming normal activity. Drinking plenty of fluids and avoiding strenuous activity for a day or two reduces the chance of a post-procedure headache. If a headache does develop and doesn’t respond to rest and hydration within a few days, your doctor can discuss a blood patch, a procedure in which a small amount of your own blood is injected into the epidural space to seal the puncture site.
The radioactive tracer clears from the body naturally, primarily through the kidneys. The radiation dose to the patient is low, and no special precautions for family members or coworkers are needed afterward. If pledgets were placed in your nose, the removal is quick and painless. Results are typically interpreted by a nuclear medicine physician, and a report goes to your referring doctor within a day or two, though the 24-hour imaging session means the final read can’t happen until at least the day after your procedure.