The research, published in the open-access journal Heliyon, was led by Christopher J. Shin and Tarik F. Massoud of Stanford University Medical Center. The team set out to answer a deceptively simple question: if engineers ever build a shunt that diverts cerebrospinal fluid directly into the skull bone instead of threading a tube all the way to the abdomen, where exactly inside the skull should such a device be placed? Their answer, drawn from high-resolution magnetic resonance imaging of forty adults, is that the largest diploic venous lakes cluster predictably near well-known surface landmarks of the skull, most notably the pterion and the asterion, and could therefore serve as anatomically reliable targets for a new generation of intraosseous drainage devices.

To understand why this matters, it helps to consider the shortcomings of the current gold standard. Long-term ventriculoperitoneal shunting, the standard treatment for communicating hydrocephalus, including idiopathic normal pressure hydrocephalus, carries a well-documented burden of complications. Shunts can become infected or obstructed, abdominal pseudocysts can form around the distal catheter, bowel perforation can occur, and overdrainage can precipitate subdural hemorrhages. For decades, neurosurgeons have sought alternatives that would keep cerebrospinal fluid within the body while avoiding the fragile plumbing of a peritoneal catheter. One idea, explored by a small group of researchers in Alberta over the past two decades, is to use the skull itself as a receptacle, allowing diverted fluid to percolate through the cancellous bone of the diploë and into the diploic veins, which ultimately deliver it to the dural venous sinuses.

That concept, however, has run into a fundamental problem. Computational fluid dynamics modeling of skull bone specimens has shown that the porosity and permeability of the diploë vary enormously from one region to another and from one patient to the next. Fluid pushed into the bone may dissipate at unpredictable rates, making it impossible to guarantee consistent drainage. The Stanford team’s hypothesis was that bypassing the spongy bone altogether and cannulating, or placing a catheter tip directly into or beside, a markedly enlarged diploic venous lake might sidestep this variability. Rather than relying on the bone as a passive reservoir, the device would tap directly into the venous highway that already connects the diploic space to the dural sinuses.

Testing that idea required a detailed anatomical map, and diploic veins are notoriously difficult to study. They cannot be dissected cleanly, they are invisible on conventional angiography, and they have been called the least studied of all the vascular networks of the head and neck. The Stanford investigators turned to a volumetric, fat-suppressed, post-contrast spoiled gradient recalled echo sequence acquired on 3 Tesla MRI scanners, with isotropic slices just 0.9 millimeters thick. Gadolinium contrast enhancement made the venous channels within the bone stand out vividly, allowing the researchers to trace their branching patterns in three orthogonal planes. They retrospectively sampled brain MRI examinations performed between May 2014 and September 2020, randomly selecting studies reported as normal or near-normal and excluding any patient whose intracranial or calvarial pathology might have altered venous hemodynamics.

The final cohort comprised forty adults, twenty-seven women and thirteen men, with a mean age of 48.4 years, drawn from a broad range of clinical indications including headache, multiple sclerosis, seizures, and cognitive symptoms. A neuroradiologist and a senior trainee reviewed every scan together on a picture archiving system, reaching consensus on each measurement. The team catalogued eighty bilateral diploic venous channels and classified their configurations into six patterns previously described by the anthropologist Israel Hershkovitz and colleagues: coronal, hybrid, bonsai, serpentine, spider, and thousand lakes. The coronal pattern was by far the most common, appearing in thirty-nine of the eighty channels, followed by hybrid and bonsai configurations. The parietal bones hosted the majority of these structures, and twenty-four subjects showed bilaterally symmetrical arrangements.

For morphometric analysis, the researchers focused on the dominant channel in each subject, defining diploic veins as channels under 3 millimeters in maximal diameter and diploic lakes as focally dilated channels measuring 3 millimeters or more. The 3-millimeter cutoff was chosen partly because it exceeds the 2.1-millimeter outer diameter of the largest 14-gauge intraosseous needle currently available clinically, meaning any lake above this threshold could in principle accommodate a cannula. Of the forty dominant channels, seventeen, or 42.5 percent, qualified as diploic lakes. Their dimensions varied dramatically: mean maximal diameter was 8.3 millimeters, but the median was only 4.2 millimeters and the largest lake reached an extraordinary 46.8 millimeters, with cross-sectional areas ranging from 4.5 to 183.8 square millimeters. This right-skewed distribution underscores how much individual anatomy can differ from person to person.

The most striking result, however, concerned location. More than eighty percent of the large-caliber channels lay within 20 millimeters of the nearest established external skull landmark, and 84.6 percent lay within 30 millimeters. The pterion, the junction where the frontal, parietal, temporal, and sphenoid bones meet, was the most frequent site of proximity, with twenty-six channels found at a mean distance of just 10.9 millimeters. The asterion, the junction of the parietal, temporal, and occipital bones near the transverse sinus, hosted only four channels, but those were almost contiguous with the landmark, at a mean distance of 0.5 millimeters. Crucially, every channel associated with the pterion or asterion lay within 20 millimeters of its landmark. By contrast, channels near the lambda, at the back of the skull, sat farthest away, averaging 64.3 millimeters. This clustering aligns with known drainage pathways: the anterior temporal diploic veins converge toward the sphenoparietal sinus near the pterion, while the posterior temporal veins connect to the transverse and sigmoid sinuses near the asterion.

Equally important for any future device design was what the study did not find. There were no statistically significant differences in vessel size between men and women, and correlations between age and vessel dimensions were negligible. This demographic stability, consistent with earlier osteological evidence, suggests that surface-based targeting strategies developed from these measurements could generalize across patients without needing to adjust for sex or age. The findings also reinforce a growing appreciation of the diploic system’s physiological significance. Beyond serving as a potential thermoregulatory radiator for the brain, the diploic veins appear to participate in cerebrospinal fluid drainage, with arachnoid granulations and lateral lacunae providing pathways by which fluid filters into the venous channels. Some anthropologists have even proposed that the evolution of the diploic system played a role in the expansion of the human brain, with similarities noted between modern humans and Neanderthals.

The authors are careful to frame their work as a foundational anatomical study rather than a clinical validation. The analysis did not assess flow dynamics, pressure gradients, or cannulation feasibility, and vessel size alone does not establish that a diploic lake can sustain cerebrospinal fluid drainage. Measurements were obtained by consensus review rather than by independent blinded readers, and the retrospective clinical cohort may not perfectly represent a healthy population. Earlier experimental work offers encouraging context, however: cadaveric infusion studies have shown that fluid injected into the diploic space rapidly reaches the superior sagittal sinus and lateral lacunae, confirming direct venous continuity, and animal models have demonstrated similarly low-resistance connections. Whether a catheter tip parked within or beside a diploic lake would outperform the surrounding diploë as a drainage receptacle remains to be proven, likely requiring bioengineering studies in large animal models, and possibly even surgically constructed venous lakes, since the human diploic system may have no perfect animal counterpart. Still, by converting a century of qualitative observation into quantitative morphometrics anchored to palpable skull landmarks, the Stanford team has given device designers, for the first time, a reproducible map of where the skull’s hidden veins are waiting.

Subject of Research: MRI-based morphometry of calvarial diploic venous lakes for designing intraosseous cerebrospinal fluid diversion devices

Article Title: MRI-derived spatial morphometrics of calvarial diploic venous lakes for designing next-generation cerebrospinal fluid diversionary devices

Article References: Shin, C. J., Bates, N. S., Decker, J. H., & Massoud, T. F. (2026). MRI-derived spatial morphometrics of calvarial diploic venous lakes for designing next-generation cerebrospinal fluid diversionary devices. Heliyon, 12(15), Article e45529. https://doi.org/10.1016/j.heliyon.2026.e45529

Image Credits: AI Generated

DOI: 10.1016/j.heliyon.2026.e45529

Keywords: diploic veins, diploic venous lakes, hydrocephalus, cerebrospinal fluid shunt, intraosseous infusion, skull anatomy, MRI, neurosurgery, pterion, asterion, ventriculoperitoneal shunt, dural venous sinuses

The story began two to three years before the young woman finally sought care. She experienced intermittent abdominal discomfort, recurrent vomiting, and mild to moderate headaches, symptoms that on their own could point in almost any direction in medicine. Then, over the final two to three months before presentation, her vision began to deteriorate in both eyes, progressively and relentlessly. Five days before she reached the outpatient department, she lost her sight entirely. By the time she was examined, she could perceive only fluctuating light in each eye. Her pupils remained equal and reactive to light, her mental functions were intact, and her limb strength was normal, but she showed subtle cerebellar signs on her left side, including an impaired finger-to-nose test and difficulty with rapid alternating movements.

Brain imaging explained much of what her examination could not. Computed tomography and magnetic resonance imaging revealed extensive, bilateral calcifications deposited in the basal ganglia, the thalami, and the dentate nuclei of the cerebellum, a distribution classic for Fahr-type intracranial calcification. Alongside these mineral deposits sat a well-defined cystic mass in the left cerebellum, with imaging features compatible with a pilocytic astrocytoma. Critically, the mass was compressing the fourth ventricle, the narrow channel through which cerebrospinal fluid drains from the brain’s interior, and the ventricles above it had dilated in response. The diagnosis was obstructive hydrocephalus, a build-up of fluid under pressure that, left untreated, is a neurosurgical emergency.

Fahr’s disease, more precisely termed primary familial brain calcification when no secondary cause can be identified, is a rare neurological disorder that most often affects young to middle-aged adults. The terminology matters: Fahr disease or PFBC refers to primary calcification without an identifiable underlying cause, while Fahr syndrome describes calcification arising secondary to another disorder, most commonly hypoparathyroidism or pseudohypoparathyroidism. In affected brains, abnormal deposits of calcium carbonate and calcium phosphate accumulate in the basal ganglia, thalamus, hippocampus, cerebral cortex, cerebellar white matter, and dentate nuclei. Clinically, these deposits are associated with movement disorders, psychiatric symptoms, cognitive impairment, and seizures. The pathogenesis is linked to disturbances in calcium metabolism and the neurovascular unit, and pathogenic variants in genes including SLC20A2, PDGFB, PDGFRB, XPR1, MYORG, and JAM2 have been implicated, several of which disrupt inorganic phosphate handling and the integrity of the blood-brain barrier.

Pilocytic astrocytoma is an entirely different entity. It is a World Health Organization Grade I glioma, a slow-growing and generally benign tumor that primarily strikes children and young adults, with a strong preference for the cerebellum. When completely resected, its prognosis is favorable. Its danger lies in location rather than biology: a cerebellar pilocytic astrocytoma can compress the fourth ventricle or the aqueduct of Sylvius, blocking cerebrospinal fluid outflow and driving intracranial pressure upward, producing exactly the progressive neurological decline this patient experienced. The coexistence of this tumor with Fahr-type calcification is extraordinarily rare, and it creates a diagnostic trap, because dense calcification can complicate radiological interpretation of posterior fossa lesions while the tumor-induced hydrocephalus demands urgent intervention.

Surgical treatment proceeded along standard lines for a posterior fossa mass with obstructive hydrocephalus. The neurosurgical team performed a suboccipital craniectomy and achieved gross total excision of the left cerebellar mass on operative assessment. When hydrocephalus persisted after the tumor was removed, the team placed a ventriculoperitoneal shunt, a catheter system that diverts excess cerebrospinal fluid from the ventricles to the abdominal cavity, a standard indication following posterior fossa tumor resection when fluid drainage fails to recover on its own. The postoperative course was uneventful. Headaches and vomiting gradually improved, and postoperative imaging showed expected surgical changes with the ventricular catheter correctly positioned. Vision, however, remained profoundly impaired.

Histopathology added an important layer of uncertainty. The resected tissue showed extensive hyalinization and regressive changes, with largely acellular material and no visible cellular areas, leading the pathologists to list pilocytic astrocytoma only as a possible differential diagnosis. This matters because regressive and degenerative features, including vascular hyalinization, calcification, and paucicellular fibrillary areas, are well recognized in pilocytic astrocytoma and can dominate the histological picture in long-standing lesions. Definitive confirmation would require the tumor’s characteristic bipolar piloid cells, Rosenthal fibers, and eosinophilic granular bodies, supported by GFAP immunohistochemistry and, where feasible, testing for the KIAA1549-BRAF fusion, which is present in approximately 90 percent of cerebellar pilocytic astrocytomas. Neither immunohistochemistry nor molecular testing was available in this case, so the tumor diagnosis remains presumptive.

The authors of the report are candid about the limits of what can be concluded. Serum calcium, phosphate, and parathyroid hormone levels were never obtained, so calcification secondary to a disorder of calcium metabolism could not be excluded biochemically, and the case cannot be firmly classified as primary familial brain calcification rather than Fahr syndrome. No family history was documented and no genetic testing was performed, leaving the calcification designation radiological rather than molecularly confirmed. Formal ophthalmologic assessment, including fundoscopy, grading of papilledema, and visual-field testing, was also unavailable, meaning the mechanism of visual loss must be inferred rather than directly demonstrated. Long-term follow-up is not yet established, and the team plans continued surveillance for visual recovery, tumor recurrence, and progression of the calcification.

The visual outcome deserves particular attention, because it carries the case’s most important clinical lesson. Posterior fossa masses rarely involve the visual pathway directly; bilateral visual failure most likely reflects raised intracranial pressure transmitted to the optic nerve heads, where sustained papilledema can produce axoplasmic stasis, ganglion cell axonal loss, and ultimately optic atrophy. Papilledema usually resolves after tumor resection or cerebrospinal fluid diversion, but deficits that are severe or long-standing at presentation may persist despite adequate treatment of the hydrocephalus, which accounts for the limited recovery observed here. Permanent visual loss is uncommon in posterior fossa tumors overall, reported in roughly 6 to 8 percent of children, and outcomes are generally most favorable for pilocytic astrocytoma, making the profound and largely irreversible deficit in this patient an atypical result. The authors argue it underscores the importance of early fundoscopic assessment and expedited cerebrospinal fluid diversion whenever visual symptoms accompany a posterior fossa mass.

How rare is this combination, really? A small number of comparable cases have been described. The first association was reported in 1984, when a patient’s scans showed Fahr-type calcification adjacent to a cystic astrocytoma. An autopsy study in 1993 identified a low-grade astrocytoma with extensive bilateral calcification and noted astrocytic proliferation near calcified deposits. In 2015, a 32-year-old woman was reported with bilateral calcification and an adjacent low-grade cystic astrocytoma, and the authors of that report observed a recurring pattern: relatively young patients with predominantly cerebellar tumors, where a cystic glioma arises next to a calcified dentate nucleus. In 2023, a coexistent meningioma broadened the reported tumor spectrum beyond astrocytoma. Current evidence suggests no established causal relationship between primary familial brain calcification and tumor development, and coexistence has generally been attributed to long-standing reactive astroglial proliferation around calcified deposits rather than a proven mechanism. Because the literature search underpinning this report was not systematic, the authors decline to assign a precise total to previously reported cases, and observations from a single patient cannot establish causation. What the case does establish is a diagnostic principle: when symptoms are progressive and disproportionate to any single diagnosis, clinicians should consider that more than one pathology may be at work, and they should match the certainty of their diagnostic language to the evidence actually available.

Subject of Research: Coexistence of Fahr-type intracranial calcification and a presumed cerebellar pilocytic astrocytoma with obstructive hydrocephalus

Article Title: Coexistence of Fahr‐Type Intracranial Calcification and a Presumed Cerebellar Pilocytic Astrocytoma With Obstructive Hydrocephalus: A Rare Case Report

Article References: Coexistence of Fahr‐Type Intracranial Calcification and a Presumed Cerebellar Pilocytic Astrocytoma With Obstructive Hydrocephalus: A Rare Case Report. (n.d.). https://doi.org/10.1002/ccr3.73552

Image Credits: AI Generated

DOI: 10.1002/ccr3.73552

Keywords: Fahr disease, primary familial brain calcification, pilocytic astrocytoma, obstructive hydrocephalus, cerebellar tumor, intracranial calcification, ventriculoperitoneal shunt, papilledema, posterior fossa, neurosurgery, SLC20A2, case report

The review, authored by a team of pediatric radiologists at Nemours Children’s Hospital in Florida, walks through the entire anatomy and engineering of shunt systems, from the proximal catheter threaded into a ventricle to the distal tubing that delivers fluid to an absorptive site in the body. Cerebrospinal fluid itself is produced mainly by the choroid plexus, specialized ependymal cells lining the ventricles, and it circulates continuously through the ventricular system and the subarachnoid spaces surrounding the brain and spinal cord before being cleared through arachnoid projections, meningeal lymphatic vessels, and the glymphatic system. When this elegant circulation breaks down, whether through obstruction, overproduction, or impaired absorption, the ventricles expand and compress the surrounding brain tissue, producing the constellation of symptoms that defines hydrocephalus.

A shunt system is deceptively simple in concept. A proximal catheter, typically made of silicone and measuring two to three millimeters in diameter, is placed within the fluid-filled space requiring diversion, most commonly a lateral ventricle. The fluid then passes through a valve that enforces one-way drainage and regulates flow according to the pressure gradient between the proximal brain compartment and the distal drainage site. Valves that respond purely to this pressure differential are called differential-pressure valves, and they may operate at a fixed preset pressure or at an adjustable setting that clinicians can reprogram noninvasively through the skin using magnetic tools. Raising the opening pressure reduces drainage and can allow the ventricles to enlarge, while lowering it increases flow, though the timing and magnitude of these changes vary considerably between patients. The review emphasizes a crucial safety point: magnetic resonance imaging can inadvertently alter programmable valve settings, so the valve must be checked promptly after every MRI scan, even though most modern designs are rated compatible up to 3 Tesla.

Where the distal catheter ends up matters enormously. The peritoneal cavity is the favored destination because its vast absorptive surface can soak up cerebrospinal fluid efficiently, making the ventriculoperitoneal shunt the workhorse of neurosurgery. But abdominal scarring, infections, necrotizing enterocolitis, or congenital gastrointestinal anomalies sometimes rule out the peritoneum. In those cases, surgeons may route the distal catheter into the right atrium of the heart, where the fluid enters the bloodstream, or into the pleural cavity surrounding the lungs. Recent meta-analyses cited in the review show that ventriculoatrial shunts, once largely abandoned in favor of the peritoneal route, now carry infection, revision, and mortality rates comparable to ventriculoperitoneal shunts. Even the gallbladder can serve as a destination in rare ventriculobiliary shunts, though the review cautions that a small pediatric gallbladder, sometimes only about 1.4 cubic centimeters in infants, limits storage capacity, and that mistaking this uncommon device for a truncated peritoneal shunt during surgery risks biliary leakage.

Imaging in the days after surgery reveals a predictable set of expected changes alongside genuine early complications. Mild pneumocephalus, air within the skull, is frequently seen and usually resolves on its own, though rarely it can progress to dangerous tension pneumocephalus. When markedly dilated ventricles collapse rapidly after shunting, fluid or blood can accumulate in the subdural compartment, and ventricular decompression may even shift the catheter tip out of the ventricle entirely. Intracranial hemorrhage, whether subarachnoid, intraventricular, or parenchymal, remains another recognized early risk that radiologists must actively exclude.

The stakes of getting imaging right are stark. Pediatric shunt failure rates reach 30 to 40 percent within the first year and approximately 50 percent by two years, according to figures compiled in the review. Non-contrast head CT is typically the first study ordered when malfunction is suspected, and low-dose protocols are preferred to limit radiation while preserving diagnostic accuracy. Increasingly, however, fast MRI protocols built around single-shot fast T2 sequences are replacing CT, offering a rapid assessment of ventricular size in minutes without sedation and without ionizing radiation, a particular advantage for children who require repeated follow-up imaging. Diffusion-weighted imaging adds another layer of power, detecting the restricted diffusion characteristic of purulent debris in ventriculitis or abscess. Still, the review stresses a humbling truth: ventricular size alone is not a reliable indicator of shunt function. Ventricles may remain stubbornly small despite malfunction in patients with poor brain compliance or slit ventricle syndrome, and changes in size may simply reflect valve reprogramming. Supporting clues include periventricular white matter edema, edema along the catheter track, and subgaleal fluid collections, though the authors warn that bright periventricular signal on T2 and FLAIR sequences must be distinguished from the normal incomplete myelination seen in very young children.

When anatomy alone cannot settle the question, functional studies take over. The traditional radiographic shunt series, frontal and lateral views of the head, chest, and abdomen, is now known to have low sensitivity and a high false-negative rate, limiting its usefulness to suspected mechanical problems such as kinking or disconnection. Shuntograms, in which contrast or radiotracer is injected into the reservoir and followed through the system, assess both patency and physiological flow; one study of 107 contrast-enhanced shunt series found a higher negative predictive value than either CT or plain radiography. Radionuclide shuntograms are especially valuable when clinical suspicion of failure persists despite normal ventricular size, and combining nuclear medicine with CT outperforms CT alone. In one striking example from the review, tracer failed to spill into the peritoneum for two hours in a teenager with headaches and seizures, prompting positional maneuvers that restored free flow, revealing that constipation, of all things, had temporarily compressed the distal catheter and raised intra-abdominal pressure. Such false-positive obstructions, the authors note, can spare patients unnecessary revision surgery if recognized.

The catalog of long-term complications reads like a textbook of applied pathology. Obstruction, the most common malfunction, usually strikes at the ventricular catheter tip, where choroid plexus and ependymal tissue grow into the fenestrations, or at the valve, which can clog with blood or debris. Infections cluster within the first six months, typically from skin flora such as Staphylococcus epidermidis and Staphylococcus aureus, with the slow-growing Cutibacterium acnes capable of smoldering undetected for longer periods. Infected ventriculoatrial shunts are particularly dangerous because contaminated fluid drains directly into the bloodstream, and a distinctive late consequence, shunt nephritis, occurs in roughly 4 to 14 percent of infected cases through immune complex deposition in the kidneys, with only about half of affected patients regaining full renal function. Abdominal pseudocysts, fibrous-walled fluid collections that encase the distal catheter, can appear anywhere from three weeks to five years after surgery. Meanwhile, growing children stretch and calcify their tubing, and fractures most often occur in the mobile neck region roughly five years after calcifications first appear, prompting the authors to recommend closer surveillance once calcification is spotted on radiographs.

Perhaps the most conceptually fascinating complications arise from the physics of drainage itself. When an upright patient’s posture increases the vertical column of fluid between brain and abdomen, a siphoning effect can overdrain the system, collapsing the ventricles into slit-like spaces and, over years, producing the notorious slit ventricle syndrome, generally flagged radiologically by a fronto-occipital horn ratio of 0.2 or less. In this state the ventricle walls collapse around the catheter, functionally obstructing it even though the hardware is patent. Anti-siphon devices help, and their introduction has also reduced rates of trapped fourth ventricle, a condition in which inflammatory scarring isolates the fourth ventricle and progressive fluid accumulation there compresses the brainstem, sometimes producing a telltale keyhole shape as the ventricle herniates upward through the tentorial hiatus. The review’s overarching message is that no single test suffices: only a nuanced, multimodality approach, pairing anatomic imaging with functional studies and a deep understanding of each patient’s hardware, allows clinicians to catch these failures early and protect the children whose lives depend on these silent, tireless tubes.

Subject of Research: Multimodality imaging evaluation of cerebrospinal fluid shunt systems and their complications in hydrocephalus

Article Title: Multimodality imaging of cerebrospinal fluid shunts: system evaluation and complications

Article References: Hoodeshenase, S., Averill, L., Mody, T., & Johnson, C. (2026). Multimodality imaging of cerebrospinal fluid shunts: system evaluation and complications. Pediatric Radiology. https://doi.org/10.1007/s00247-026-06759-z

Image Credits: AI Generated

DOI: 10.1007/s00247-026-06759-z

Keywords: hydrocephalus, cerebrospinal fluid shunt, ventriculoperitoneal shunt, shunt malfunction, pediatric radiology, neuroimaging, shunt infection, slit ventricle syndrome, radionuclide shuntogram, MRI, shunt obstruction, trapped fourth ventricle