Brain tissue does not develop literal empty holes the way a piece of wood might, but a wide range of conditions can destroy, soften, or displace brain matter in ways that look like cavities on a scan. The colloquial phrase “holes in the brain” usually refers to cysts, areas of dead or softened tissue after a stroke or injury, lesions from infections or parasites, the sponge-like damage of prion diseases, or the dark spots seen in multiple sclerosis. Because so many different problems can produce these findings, treatment depends entirely on the underlying cause.
What People Actually See on a Brain Scan
When a doctor points to a dark or fluid-filled area on an MRI or CT and a patient hears the word “hole,” what they are usually looking at is one of a few things: a cyst filled with cerebrospinal fluid, a pocket of dead tissue that has been replaced by fluid, or a region where the brain’s normal structure has broken down. These show up as dark or bright spots depending on the type of scan. Radiologists use the location and signal characteristics to narrow down the cause, because most intracranial cysts tend to appear in fairly predictable anatomical spots. For instance, distinguishing whether a cystic lesion sits inside the brain tissue itself or in the space surrounding it is one of the first steps in building a differential diagnosis.1PubMed. Imaging of Intracranial Cysts
Advanced MRI techniques, including diffusion-weighted imaging, can help tell the difference between a brain abscess and a cystic tumor, two conditions that can look nearly identical on standard scans. Calculating something called the apparent diffusion coefficient from those images has been shown to distinguish abscesses from necrotic tumors with perfect specificity in at least one study.2PubMed. Differential MRI diagnosis between brain abscesses and necrotic or cystic brain tumors using the apparent diffusion coefficient and normalized diffusion-weighted images
Cysts
Arachnoid cysts are the single most common type of intracranial cystic lesion found on imaging. They are fluid-filled sacs that form between the brain and the membrane covering it, and the majority are congenital, meaning they develop before birth. Most are discovered incidentally when someone gets a scan for an unrelated reason, and they never cause symptoms. Other cyst types, including those of infectious or vascular origin, are less common but can mimic arachnoid cysts on initial imaging.3PubMed Central. Non-neoplastic intracranial cystic lesions: not everything is an arachnoid cyst
When an arachnoid cyst does cause problems, usually because it is large enough to press on surrounding structures, surgical options include fenestration (creating openings in the cyst wall so fluid drains into normal pathways) or placing a shunt to redirect fluid to the abdominal cavity. A comparative study in pediatric patients found that microsurgical fenestration, endoscopic fenestration, and cyst-to-peritoneum shunts are all used, with the choice depending on cyst location and the surgeon’s judgment.4PubMed Central. Intracranial arachnoid cysts: What is the appropriate surgical technique? A retrospective comparative study with 61 pediatric patients Endoscopic approaches have also been used for more complex situations like multi-compartment fluid collections in children with hydrocephalus, where fenestrating internal walls helps restore normal fluid circulation.5PubMed. Treatment of multi-loculated hydrocephalus using endoscopic cyst fenestration and endoscopic guided VP shunt insertion
Stroke and Small Vessel Disease
Stroke is probably the most common reason an adult develops a visible cavity in the brain. When blood supply to a region is cut off, the tissue dies. Over time, the body clears away the dead cells, leaving behind a fluid-filled space or a patch of softened, scarred tissue called encephalomalacia. This process is especially well documented after large strokes, but it also happens on a smaller scale with lacunar infarcts, the tiny strokes caused by disease in the brain’s small penetrating arteries.
Two distinct vascular problems drive lacunar damage. The walls of small arteries can thicken, reducing blood flow to deep brain structures like the basal ganglia and thalamus. Separately, plaque buildup in larger parent arteries can block the mouths of these tiny vessels. Both pathways starve downstream tissue and can also cause fluid leakage that damages the surrounding white matter over time.6PubMed Central. Lacunar infarction and small vessel disease: pathology and pathophysiology
Treatment for stroke-related brain cavities focuses on preventing further damage rather than reversing what has already happened. Blood pressure control, cholesterol management, anticoagulants or antiplatelet drugs where appropriate, and lifestyle changes form the backbone of secondary prevention. The cavity itself is permanent, but rehabilitation (discussed further below) can help the brain compensate.
Encephalomalacia from Trauma
A severe blow to the head can also kill brain tissue and produce encephalomalacia, though this is more commonly discussed in the context of strokes. Case reports of trauma-induced encephalomalacia in adults are uncommon enough to be considered clinically noteworthy when they do appear. In documented cases, symptoms have been attributed to tissue softening in specific lobes, confirmed by both CT and MRI.7PubMed Central. Encephalomalacia from Physical Trauma in an Adult: A Case Report and Review of Literature The damaged tissue cannot be restored, so treatment involves managing symptoms like seizures, cognitive problems, or motor deficits, along with rehabilitation.
Infections and Parasites
Bacterial brain abscesses are pockets of pus that form when infection takes hold inside the skull. Even after successful antibiotic treatment, the abscess site often leaves lasting damage. Imaging studies done years after treatment have found reduced metabolic activity in the cortex surrounding the former abscess, indicating long-term tissue injury.8PubMed Central. Bacterial Brain Abscesses Expand Despite Effective Antibiotic Treatment: A Process Powered by Osmosis Due to Neutrophil Cell Death In a separate study evaluating patients a year or more after neurosurgical drainage, all showed some degree of tissue loss and scarring at the abscess site.9PubMed Central. Brain Abscess Causes Brain Damage With Long-Lasting Focal Cerebral Hypoactivity that Correlates With Abscess Size The practical message is that while antibiotics and surgery can cure the infection, the “hole” left behind is often permanent.
Parasitic infections add another dimension. Neurocysticercosis, caused by the larval stage of a pork tapeworm, is one of the most common causes of seizures worldwide in regions where the parasite is endemic. The larvae form cysts in the brain that can sit quietly for years or trigger inflammation as they degenerate.10PubMed Central. Clinical symptoms, diagnosis, and treatment of neurocysticercosis Treatment decisions are highly individualized. Consensus guidelines recommend basing the choice on the number, location, and viability of the parasites, and they emphasize that dangerous pressure buildup inside the skull must be addressed before anything else.11PubMed Central. Current consensus guidelines for treatment of neurocysticercosis Two antiparasitic drugs, albendazole and praziquantel, are the main options, though available evidence has not conclusively established one as superior to the other.12PubMed Central. Antiparasitic drugs in neurocysticercosis: albendazole or praziquantel?
Prion Diseases and the “Sponge Brain” Pattern
Prion diseases like Creutzfeldt-Jakob disease (CJD) are the conditions that most literally earn the description “holes in the brain.” Under a microscope, affected tissue is riddled with tiny vacuoles, giving it a sponge-like appearance, which is why these illnesses are called transmissible spongiform encephalopathies. The damage is driven by misfolded prion protein that accumulates in the spaces between brain cells, eventually killing neurons.13Micron. Pathology of the transmissible spongiform encephalopathies with special emphasis on ultrastructure Research has found that this vacuolation tends to cluster near blood vessels, likely because factors in the vessel walls promote prion protein aggregation rather than because the disease spreads through the bloodstream.14PubMed. Spatial correlations between the vacuolation, prion protein (PrPsc) deposits and the cerebral blood vessels in sporadic Creutzfeldt-Jakob disease
There is no cure for prion diseases. They progress rapidly and are universally fatal, typically within a year of symptom onset for CJD. Treatment is entirely supportive, focused on comfort and managing symptoms like involuntary movements or agitation. The rarity and speed of these diseases have made therapeutic research exceptionally difficult.
Multiple Sclerosis “Black Holes”
People with multiple sclerosis (MS) develop lesions throughout the brain’s white matter as the immune system attacks the protective myelin coating of nerve fibers. Some of these lesions appear as dark spots on certain types of MRI scans, earning them the nickname “black holes.” These dark areas can represent temporary swelling or, more ominously, permanent tissue destruction with loss of the nerve fibers themselves.15PubMed. Evolution of T1 black holes in patients with multiple sclerosis imaged monthly for 4 years
Not all black holes are permanent. A study tracking MS patients monthly for four years found that roughly 56% of acute black holes evolved into persistent ones, meaning the rest resolved over time as inflammation settled.15PubMed. Evolution of T1 black holes in patients with multiple sclerosis imaged monthly for 4 years Encouragingly, research using quantitative MRI has shown that when tissue recovery does occur in black holes, it correlates with clinical improvement.16PubMed Central. T1 Recovery Is Predominantly Found in Black Holes and Is Associated with Clinical Improvement in Patients with Multiple Sclerosis Disease-modifying therapies for MS aim to reduce new lesion formation and slow the accumulation of permanent damage, though they cannot erase existing black holes.
Congenital Conditions
Some babies are born with cavities in the brain due to events that occurred during fetal development. Porencephaly, a condition in which fluid-filled cysts or cavities communicate with the brain’s ventricles, can result from vascular disruptions in utero. This has been particularly documented in monozygotic (identical) twins, where the death of one twin may send embolic material or clotting factors through shared placental blood vessels to the surviving twin, destroying developing brain tissue.17Pediatrics. Congenital Hydranencephaly/Porencephaly Due to Vascular Disruption in Monozygotic Twins Hydranencephaly, a more severe version in which most of the cerebral hemispheres are replaced by fluid, can arise from the same mechanism. Treatment for these conditions is supportive and may involve shunting to manage fluid buildup, but the lost brain tissue cannot be replaced.
Toxic Exposures and Radiation
Certain toxins can destroy specific brain regions. Carbon monoxide poisoning, for example, has a well-known tendency to damage the basal ganglia, the deep brain structures involved in movement. CT scans of survivors have revealed calcified lesions in these areas even decades after the initial poisoning event.18Neuroradiology. Calcification of the basal ganglia following carbon monoxide poisoning Alcohol abuse, certain recreational drugs, and industrial chemical exposures can also cause brain tissue loss, though the patterns vary.
Radiation therapy for head and neck cancers or brain tumors can itself damage the brain. Delayed radiation necrosis, where brain tissue dies months or years after treatment, is a recognized complication. It can produce a mass-like lesion that mimics tumor recurrence on imaging, making diagnosis tricky.19PubMed Central. Conservative treatment of delayed cerebral radiation necrosis Some cases resolve with conservative management, but others require surgery to relieve pressure or steroids to reduce swelling.
Enlarged Perivascular Spaces
Not every “hole” on a brain scan is cause for alarm. Perivascular spaces are fluid-filled channels that surround the small blood vessels penetrating the brain. They are a normal part of anatomy and serve as drainage pathways. When they become enlarged, they show up on MRI as tiny bright or dark dots, and they can look alarming to someone not accustomed to reading brain scans. Enlarged perivascular spaces become more common with aging and high blood pressure.
Recent research has linked these spaces to the brain’s waste-clearance system, sometimes called the glymphatic system. The idea is that cerebrospinal fluid flows in along arteries and out along veins, flushing metabolic waste as it goes. When this system falters, perivascular spaces may enlarge as fluid backs up.20PubMed Central. Perivascular spaces, glymphatic dysfunction, and small vessel disease A 2025 study that tracked the flow of a contrast agent through the brain after spinal injection provided some of the first direct human evidence for this directional flow pattern. It found that enlarged venous perivascular spaces in the basal ganglia were independently associated with lower cognitive scores, even after accounting for age and education level.21PubMed. Deep Venous Perivascular Space Dysfunction Reflects Glymphatic Aging and Predicts Cognitive Vulnerability: In Vivo Human Evidence Enlarged perivascular spaces do not require treatment on their own, but they may signal underlying vascular risk factors worth managing.
Rehabilitation and How the Brain Compensates
Regardless of what caused the damage, the brain has a remarkable capacity to reorganize after injury. This process, broadly called neuroplasticity, involves surviving neurons forming new connections, sprouting new branches, and sometimes recruiting neighboring regions to take over functions lost when tissue was destroyed.22PubMed Central. Adaptive Neuroplasticity in Brain Injury Recovery: Strategies and Insights Rehabilitation strategies, including physical therapy, occupational therapy, speech therapy, and cognitive exercises, are designed to harness this plasticity and push the brain toward adaptive rather than maladaptive reorganization.23PubMed Central. A comprehensive review on adaptive plasticity and recovery mechanisms post-acquired brain injury
The window for recovery is widest in the first months after injury, but plasticity continues at a slower rate for years. The degree of recovery depends heavily on the size and location of the damage, the person’s age, and how aggressively rehabilitation is pursued. A small cavity in a non-critical area may produce no lasting symptoms at all. A large one in a region responsible for language or movement may require years of therapy to achieve partial recovery. No rehabilitation program can regenerate the lost tissue, but the functional improvements that come from rewiring can be substantial.
Experimental Approaches to Brain Tissue Repair
One of the most active frontiers in neuroscience research is the attempt to actually fill in lost brain tissue rather than just work around it. Hydrogel-based biomaterials, essentially injectable scaffolds that can carry stem cells or therapeutic molecules directly into a stroke cavity, have shown promise in laboratory settings. The idea is to provide a physical support structure that keeps transplanted cells alive long enough to integrate with surrounding tissue.24PubMed Central. Hydrogel-based biomaterials for brain regeneration after stroke: Gap to clinical translation
Animal studies have demonstrated that transplanting neural stem cells within a hydrogel matrix into the infarct cavity after a stroke significantly improved cell survival compared to injecting cells alone. The hydrogel also appeared to reduce the inflammatory response that normally kills most transplanted cells.25PubMed Central. Hydrogel matrix to support stem cell survival after brain transplantation in stroke Carrier-based hydrogels that deliver both drugs and cells to targeted brain regions are being explored as a way to enhance the approach further.26Bioactive Materials. A review: Carrier-based hydrogels containing bioactive molecules and stem cells for ischemic stroke therapy None of this has made it to routine clinical use yet, and the gap between encouraging animal results and a viable human therapy remains wide. But for the first time, the goal of regenerating damaged brain tissue has moved from science fiction into plausible translational research.