Leptomeningeal Cyst

What is Leptomeningeal Cyst?

A leptomeningeal cyst (LMC) is a distinct mass or lump that often shows up in infants who’ve had skull fractures. Howship was the first to describe it in 1816, but over time, it’s been given different names. These names include:

• Traumatic ventricular cysts.
• Cranio-cerebral erosions.
• Cranial malacia.
• Diploic cyst.
• Growing skull fracture.
• Cerebrocranial erosion.

Though it’s named as a cyst, a leptomeningeal cyst isn’t actually a cyst. Instead, it’s an encephalocele, which is a type of hernia where brain tissue, cerebral spine fluid (CSF), and leptomeningeal layers (layers protecting the brain and spine) protrude out of a defect in the skull.

These cysts develop thanks to a certain type of skull fracture that impacts both the inner and outer bone layers and injures the dura mater, which is the outermost layer of the brain and spinal cord. This type of fracture, known as a diastatic fracture, is when the connections between the skull bones widen. It’s a rare complication in infants and young children with skull fractures.

A version of this called post-traumatic intradiploic leptomeningeal cysts occurs when the fracture only affects the inner bone layer and tears the dura mater, leading to CSF accumulating in a sac. Although the sac is lined by arachnoid membrane, it isn’t the same as an arachnoid cyst. These cysts usually appear in infants; it’s thought that the rapid brain growth in this phase plays a role in forming these masses.

The typical cause is a tear in the dura mater that goes along with a linear skull fracture. This tear leaves a gap that lets the content inside the skull to protrude outwards, putting pressure on the surrounding skull. This pressure wears away the bone around the fracture, causing it to expand. The presence of the protruding tissue hampers osteoblasts (cells that form new bone) from migrating, thereby making it harder for the fracture to heal. Continual cerebral spine fluid pulse enlarges the cyst, causing it to move to the subgaleal space, an area between the skull and scalp. Both the seriousness of the trauma and the degree of diastasis, or width of the fracture (>4 mm), seem to be significant factors, too.

What Causes Leptomeningeal Cyst?

LMC, or leptomeningeal cysts, are most commonly caused by accidents like falls. These cysts usually develop in the parietal bone, which is located on the side of your skull

Some medical reports have indicated that these cysts can also occur after certain type of reconstructive surgeries on the face or skull, including surgeries to correct craniosynostosis – a condition where the joints between the bones of a baby’s skull close prematurely. These surgeries might involve a simple suturectomy (where they remove the affected suture) or even involve more extensive reshaping of the skull.

In some cases, LMCs have also been linked to the use of endoscopes – a long, flexible tube that is used to look inside the body. Also, although it is very rare, LMCs have been noticed in newborns after using vacuum extraction – a technique sometimes used to assist in the delivery of a baby.

Risk Factors and Frequency for Leptomeningeal Cyst

Leptomeningeal cysts (LMC) affect about 0.05% to 1.6% of the population. They are most common in children under the age of three. This could be due to several factors:

• The brain and skull grow quickly during this time.
• The outer layer of the brain sticks closely to the bone.
• Young children’s skulls are thin and can easily change shape.

A study found that the average age when the trauma leading to the cyst occurs is 8.8 months, but the average age when it’s first observed is 21.9 months. Boys are slightly more likely to develop these cysts. Adults rarely have LMC and if they do, it’s almost always tied to a past head injury.

Signs and Symptoms of Leptomeningeal Cyst

Scalp swelling is often the first sign noticed by parents or caregivers. The lump might feel soft or hard, depending on what’s inside it. Most people experience a gradual increase in the swelling, which is not painful. Other symptoms can vary widely and may include:

• A mass on the scalp that pulsates and worsens with coughing or crying
• Headaches
• Loss of consciousness
• Seizures
• Neurological problems, such as trouble moving or feeling sensations
• Vision problems, crossed eyes, or bulging eyes
• Developmental delays
• Obvious abnormal shape of the skull

In children who are diagnosed later, loss of consciousness and neurological problems are quite common. Sometimes, the condition can advance and cause new seizures or other neurological problems. In adults, the swelling may be associated with headaches and abnormal sensations on the scalp.

A study involving 440 patients found that the average age at diagnosis was around 22 months and the majority of patients were male. Another study found that most patients had their first injury before the age of three. Seizures were reported in about 42% of cases. The time between the initial injury and the onset of symptoms can vary greatly, from less than six months to more than twenty years.

Testing for Leptomeningeal Cyst

When a doctor suspects a brain injury, a medical history check and effective imaging tools such as X-rays, computed tomography (CT), and magnetic resonance imaging (MRI) are crucial for diagnosis. These techniques help determine the severity and location of the injury, plan for surgery if needed, and rule out other diseases.

X-rays of the skull in the early phase of injury may show a diastatic fracture, a condition where a fracture line runs along a suture in the skull. In later stages, X-ray may highlight bone damage characterized by eroded edges.

A CT scan of the brain can show more details upon injury. In the early stages, it can detect concurrent injuries, like brain bruises. In its later stages, a CT scan can reveal conditions such as leptomeningeal cyst (a type of brain cyst), intradiploic cyst (a cyst within the skull bone), damage to the brain tissue (encephalomalacia), porencephalic cyst (brain tissue replaced by a fluid-filled cavity), uneven brain ventricles, and brain fluid accumulation (hydrocephalus). 3D CT scans can help to identify the fracture patterns more accurately.

An MRI scan provides even more detailed images and can help to identify, at an early stage, any defects in the dura (the tough outermost layer enveloping the brain and spinal cord) and any herniated brain elements (displacement of brain tissue). Particularly amongst patients with symptoms like cephalhematoma (a condition where a blood clot forms underneath a newborn’s scalp), a bone diastasis (separation) of 4 mm or more, and underlying brain bruising should have an MRI with a contrast agent to identify any dural tear and brain herniation.

Color Doppler imaging, which uses ultrasound to visualize blood flow, can be useful especially in newborns who develop brain cysts following birth trauma. This technique can also reveal the movement of arterial blood flow, excluding conditions such as avascular masses like a cephalhematoma or subgaleal bleeding (bleeding between the scalp and the skull). It can also assist in assessing any accompanying venous (vein) injuries. In the event of seizures, an electroencephalogram, a test that detects electrical activity in the brain, could be necessary.

There are three main types of leptomeningeal cysts (brain lesions involving the meninges, the membranes that cover the brain).
Type 1 contains a leptomeningeal cyst in the skull defect.
Type 2 contains damaged and scarred brain tissue in the defect.
Type 3 features a porencephalic cyst located in a layer under the skin of the scalp.

Treatment Options for Leptomeningeal Cyst

Identifying and treating brain conditions like a leptomeningeal cyst early on is really important to prevent long-term damage to the nervous system. The main way doctors treat this condition is by performing a craniotomy, a surgical procedure where they open up the skull. They will then remove the cyst, fix the tear in the dura mater (the membrane that covers your brain and spinal cord), and use a bone graft to repair any bone defects.

In certain cases, doctors might use a collagen fleece, which mimics the late stages of the body’s natural clotting process, instead of repairing the dura mater. This material dissolves when it comes into contact with bleeding wounds or bodily fluids, helping to bridge the gap between the fleece and the wound surface.

Of course, the best solution is to close up the dural defect completely, but sometimes the cyst can come back (this happens about 2% of the time). Certain factors can make it more likely for the cyst to return, such as having a specific combination of developmental disorders that affect the skull (syndromic craniosynostosis), having increased pressure in the skull, needing repeated surgeries, or if the initial repairs to the skull and/or dura weren’t successful.

During the first surgery for craniosynostosis, a condition where the sutures in a baby’s head fuse too early, a drug called mannitol can be used. This helps to relax the brain, reducing the chance of damaging the dura.

Another important part of treating a leptomeningeal cyst is managing any extra pressure in the skull (intracranial pressure). That can be done surgically by removing any brain tissue that’s protruding and treating a condition called hydrocephalus, where fluid builds up in the brain. Doctors usually wait to do this until brain imaging can identify the brain tissue that needs to be removed. The procedure is put off until swelling goes down and the brain tissue pulls back from the defect, but if the tissue is still protruding despite monitoring and waiting (usually up to two months), the non-functional tissue has to be removed. After this point, it’s unlikely that the cyst will shrink on its own and will typically continue to grow without treatment.

There are other ways doctors can treat elevated pressure in the skull or hydrocephalus. One of these is a ventriculoperitoneal (VP) shunt, a special device that drives fluid away from the brain. Particularly, for those with hydrocephalus, using a VP shunt can sometimes be the sole treatment for repeated cysts. To repair the skull, doctors usually use a bone graft secured with absorbable screws and plates or sutures. Yet, a split-thickness graft (a graft that includes the epidermis and part of the dermis) can also be used.

When it comes to treating a leptomeningeal cyst, there are a few key steps:

1. Identify the edges of the bone defect
2. Perform a wide craniotomy to expose the dura mater defect
3. Remove the meningo-cerebral cicatrix, a scar-like tissue
4. Make sure the closure of the dura mater is watertight
5. Repair the bone defect

It’s really important to close the dural defect in a way that prevents leaking and to fix the skull. Dural defects can be, on average, around 1.42 times bigger than defects in the bone, so it is crucial to fully expose the edges of the dura mater defect. The cyst is then removed, and any damaged brain tissue is safely taken out. Doctors often use grafts from the patient’s own body, like the pericranium (the outer layer of the skull) and the fascia lata (a layer of connective tissue in the thigh), to help close the dural defect. These have shown to lead to better results because they are compatible with the patient’s tissue and reduce the risk of infections, adhesions, and rejections. For children under three, a split calvarial bone graft is recommended, although this can increase the risk of bone resorption, or the breakdown and absorption of bone tissue. Titanium mesh is often used for skull repairs thanks to its biocompatibility, low infection rate, and durability. They also use endoscopic-assisted duraplasty, a procedure to repair the dura mater, with a collagen matrix.

When it comes to orbital roof repair, which is required for certain types of a leptomeningeal cyst, it’s important to avoid surgically intervening in lesions that are located near major dural venous sinuses, which are large veins in the brain.

What else can Leptomeningeal Cyst be?

When a doctor is looking at a patient with head or brain symptoms, they might need to rule out a range of conditions. These possible diagnoses can include:

• Arachnoid cyst (a fluid-filled sac in the brain)
• Intradiploic encephalocele (brain tissue has moved into a hole in the skull)
• Lipomas caused by head injury
• Meningeal melanocytoma (a rare form of brain tumour)
• Failure of the parietal bone to form correctly from birth (congenital absence)
• Menkes disease (a rare genetic disorder)
• Eosinophilic granulomas (a type of inflammation)
• Langerhans cell histiocytosis (a disease where certain white blood cells grow)
• Multiple myelomas (types of blood cancer)
• Epidermoid cyst (a benign, rare type of tumour)
• Osteomyelitis (bone infection)
• Calvarial metastasis (spread of cancer to the skull bone)

These conditions all show up in different ways on brain scans. For example, an epidermoid cyst shows as areas of similar density to the fluid that surrounds the brain and spinal cord. In contrast, multiple myeloma shows as ‘punched-out’ holes of varying sizes throughout the skull, without any hardening (sclerotic rims) around them.

These all have different features – osteomyelitis results in bone destruction and thickening of the tissue that lines the bones, whereas skull metastases can look harder (sclerotic), softer (lytic), or a mix of the two, depending on the type of cancer.

Some conditions, like intradiploic arachnoid cysts, might come from problems with the way fluid drains from certain cells in the brain. Others, like cephaloceles, come from defects in the skull present from birth that allow different types of tissue to push through. The specific type of cephalocele is named based on what tissues are involved in the herniation, whether it’s just the meninges and cerebrospinal fluid, or if it also includes brain tissue and even the ventricles of the brain.

What to expect with Leptomeningeal Cyst

A leptomeningeal cyst is a benign (noncancerous) condition that usually has a favorable outcome. However, it’s crucial to detect and repair it quickly to prevent long-term complications. Sometimes, this cyst doesn’t cause any signs or symptoms, but even in these cases, it must be treated to avoid it growing larger and causing permanent nervous system complications.

Additionally, conditions such as epilepsy, brain herniation which can result in neurological deficits, and mental retardation might arise related to this cyst. These complications can seriously decrease the quality of life and increase the risk of other health problems.

Positive results are usually seen in most patients, even if treatment starts later than usual. In a study conducted with 440 patients, a certain type of surgery, known as dura-cranioplasty, was carried out in 61.6% of patients. This surgery helped improve seizures and neurological deficits in 12.7% and 7.05% of the cases, respectively.

However, a few factors were found in a study that may lead to less favorable outcomes:

* A significant bony defect (greater than 7 cm).
* Severe initial head injury.
* Skull defects crossing the midline.
* Delayed repair (greater than 8 months).

In addition, a type of fracture known as “comminuted” and the degree of a condition known as “diastasis” played a significant role in the development of growing skull fractures.

Children at risk of developing these growing skull fractures should be clinically monitored for up to 3 months following the initial injury. If a child has a swollen, blood-filled area on the head that lasts longer than two weeks after an injury, it’s important to stay vigilant as this could be a sign of a more serious condition.

Possible Complications When Diagnosed with Leptomeningeal Cyst

There are several complications that can occur after a procedure related to brain surgery or brain abnormalities. Here is a simplified list of what could potentially go wrong:

Main Complications:

• Bursting and subsequent collection of cerebrospinal fluid beneath the scalp
• Enlargement of the ventricle on the same side of the brain
• Buildup of cerebrospinal fluid within the brain, which can cause pressure and swelling (also known as hydrocephalus)
• Seizures
• Progressive worsening of neurological functions
• Mental retardation

Complications after Brain Surgery:

• Infection of the surgical wound
• Collection of fluid between the brain and the skull (subdural hygroma)
• Leaks of cerebrospinal fluid and brain infections (meningitis)
• Potentially life-threatening bleeding complications due to the brain sinking and tearing veins
• Recurrence of the original problem
• Risks of death due to effects of anesthesia and brain infection

Preventing Leptomeningeal Cyst

Patients should learn about the cause, progression, and surgical treatment of the leptomeningeal cyst, which is a fluid-filled sac in the brain. This type of cyst is harmless. If a child is affected, their family should understand the potential complications and know to promptly seek medical attention if the child’s health changes. While there is a small chance that the cyst may return, it is very uncommon.

It’s important to know that medical experts from different fields, such as neurosurgeons, neurologists, and pediatricians, will be involved in the patient’s care and regular follow-ups. Families should also be informed about potential long-term neurological challenges that may take a long time to improve or have an unpredictable outcome, such as intellectual disabilities, muscle weakness, speech issues, and visual problems. They should be offered the necessary support services for these challenges.

Parents’ careful observation and education plays a crucial role, especially in early detection and immediate diagnosis. Swift surgery is also key. After the operation, babies may be fitted with a helmet to help prevent the return of the cyst.