Case Study: Post-Traumatic Headache and Dizziness in a 6-Year-Old Boy, Arachnoid Cyst

Arachnoid Cyst in the Middle Cranial Fossa with Post-Traumatic Symptoms

1. Cause and Etiology

Arachnoid cysts are benign, fluid-filled sacs within the arachnoid membrane, one of the three layers of the meninges surrounding the brain and spinal cord. They are typically filled with cerebrospinal fluid (CSF) and may be:

Congenital (Primary): The majority are thought to arise from developmental anomalies during embryogenesis, such as splitting or duplication of the arachnoid membrane.
Acquired (Secondary): Less commonly, cysts may form due to trauma, infection, hemorrhage, or post-surgical changes that create a CSF-filled cavity within or between arachnoid layers.

In the case of post-traumatic symptoms, trauma often does not cause the cyst de novo but rather provokes symptoms from a preexisting cyst by:

Rupture or hemorrhage into the cyst
Rapid expansion due to CSF dynamics
Increased intracystic pressure
Mass effect on adjacent structures

2. Pathophysiology

Arachnoid cysts do not communicate freely with the subarachnoid space, which can allow fluid accumulation.
In the middle cranial fossa, the cyst can compress the temporal lobe, mesial structures, or optic pathway, depending on size and exact location.
Trauma may alter CSF circulation or induce bleeding within or around the cyst, enlarging it and increasing pressure on adjacent brain tissue.
Expansion of the cyst may lead to:

Elevated intracranial pressure
Temporal lobe dysfunction
Visual disturbances or seizures

3. Epidemiology

Incidence in the general population: ~1–2% on brain MRI.
Most common in children and young adults; male predominance.
The middle cranial fossa (Sylvian fissure region) is the most frequent site (up to 50% of all arachnoid cysts).
Often asymptomatic, but up to 20–30% may present with symptoms due to size or complications.

4. Clinical Presentation (Especially Post-Traumatic)

In cases where a previously asymptomatic cyst becomes symptomatic after minor head trauma, patients may experience:

Headache (persistent or worsened)
Dizziness or vertigo
Nausea, vomiting
Seizures
Focal neurological deficits (e.g., visual field cuts if optic pathways are involved)
Cognitive or behavioral changes
Symptoms of increased intracranial pressure (ICP): drowsiness, papilledema

5. Imaging Features

Modality of choice: CT and MRI

CT Scan:

Well-defined, hypodense (CSF density) lesion
No enhancement or calcification
Possible mass effect (e.g., effacement of temporal horn, midline shift)
Bony remodeling of the adjacent skull in chronic cases

MRI:

T1: Hypointense (similar to CSF)
T2: Hyperintense
FLAIR: No signal (unless proteinaceous or hemorrhagic)
DWI: No restricted diffusion (helps distinguish from epidermoid cyst)
No enhancement with gadolinium

Post-traumatic complications may include:

Hemorrhage within the cyst (hyperintensity on T1)
Subdural hygroma or hematoma
Enlargement or cyst rupture

6. Treatment

Treatment depends on symptom severity, cyst size, and evidence of mass effect.

🔹 Observation (Asymptomatic or minor symptoms)

Regular clinical and radiological follow-up (MRI)
No surgery unless progression

🔹 Surgical Intervention (Indicated if symptomatic or progressive)

Microsurgical fenestration (open craniotomy)

Creating communication with the subarachnoid space

Endoscopic fenestration

Minimally invasive, increasingly preferred

Cystoperitoneal shunting

Used in select cases with hydrocephalus or failure of fenestration

7. Prognosis

Generally excellent prognosis with proper management
Most patients recover well after surgical intervention
Recurrence is rare but possible, especially in shunted patients
Without intervention, large symptomatic cysts may lead to:

Chronic increased ICP
Cognitive delay (especially in children)
Seizure disorders
Visual impairment

Summary

Aspect	Summary
Etiology	Mostly congenital; trauma can provoke symptoms
Pathophysiology	CSF-filled cyst compresses adjacent structures
Epidemiology	~1–2% population; middle cranial fossa most common
Symptoms	Headache, dizziness, seizures, increased ICP
Imaging	CSF-like signal, mass effect, no enhancement
Treatment	Observation or surgical fenestration/shunting
Prognosis	Excellent with intervention; poor if untreated and large

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Case Study: Post-Traumatic Headache and Dizziness in a 6-Year-Old Boy

Arachnoid Cyst

History and Imaging

A 6-year-old boy presented with persistent headache and dizziness lasting for two days following a minor head injury sustained while playing at a playground.
There was no significant past medical history or family history, and his developmental milestones were within normal limits.
Neurological examination revealed a clear mental status, but the patient complained of nausea and demonstrated reduced visual attention.
Physical examination showed no external signs of trauma, and his vital signs, including temperature, were within normal ranges.
Brain computed tomography (CT) was performed for further evaluation.

On the axial CT image at the level of the suprasellar region, a well-demarcated hypodense lesion was identified in the left middle cranial fossa (temporal fossa).
The lesion demonstrated clear margins and showed attenuation characteristics similar to cerebrospinal fluid (CSF).
There was evidence of mass effect on the adjacent brain parenchyma.

Quiz

Q1. What is the most likely diagnosis for the well-demarcated low-density lesion identified on the CT scan?
① Chronic subdural hematoma
② Epidermoid cyst
③ Arachnoid cyst
④ Vascular malformation

Explanation: The lesion presents with a well-defined border and CT attenuation similar to cerebrospinal fluid (CSF), which is characteristic of an arachnoid cyst. While chronic subdural hematoma may occur post-trauma, it usually exhibits a crescentic shape with evidence of bleeding and encapsulation.

Q2. Which of the following is not a typical clinical manifestation of an arachnoid cyst?
① Headache
② Seizures
③ Muscle spasms
④ Asymptomatic presentation

Explanation: Arachnoid cysts are often asymptomatic or may cause nonspecific symptoms such as headache, dizziness, or seizures. Focal muscle spasms are not commonly associated with arachnoid cysts and are considered atypical.

Q3. What is the most plausible reason for a previously asymptomatic arachnoid cyst to become symptomatic following trauma?
① Intracystic infection
② Sudden enlargement of the cyst
③ Intracystic hemorrhage
④ CSF leakage due to cyst rupture

Explanation: Trauma may increase the internal pressure of an arachnoid cyst, leading to its expansion and resulting in significant compression of adjacent brain structures, thereby producing symptoms.

Findings and Diagnosis

Radiologic Findings:

A well-defined, low-density cystic lesion is observed in the left middle cranial fossa.
The lesion demonstrates attenuation similar to CSF on CT imaging.
There is evidence of mass effect, with compression of adjacent brain parenchyma.

Final Diagnosis:
Arachnoid cyst in the left middle cranial fossa, symptomatic after minor head trauma.

Differential Diagnosis

Chronic Subdural Hematoma
- Common after trauma; typically crescent-shaped with encapsulated fluid.
- CT density may be slightly higher or lower than CSF and often has irregular borders.
Epidermoid Cyst
- Also appears hypodense but typically more irregular in shape than arachnoid cysts.
- Shows restricted diffusion on diffusion-weighted MRI (DWI), unlike arachnoid cysts.
Porencephalic Cyst
- Often associated with a history of prior brain injury (e.g., infarction, hemorrhage).
- Communicates directly with the brain parenchyma and is not confined to the arachnoid layer.
Enlarged Perimesencephalic Subarachnoid Space
- Bilateral and symmetrical without focal mass effect.
- Represents a benign anatomic variant rather than a true cystic lesion.

Discussion

Post-Traumatic Symptomatic Arachnoid Cyst in the Left Middle Cranial Fossa

Arachnoid cysts are benign, CSF-filled lesions within or beneath the arachnoid membrane. Most are congenital in origin, though acquired forms may result from head trauma, infection, or hemorrhage. In the current case, the patient developed a headache and dizziness following minor trauma, and brain imaging revealed an arachnoid cyst in the left middle cranial fossa.

Although many arachnoid cysts remain asymptomatic, they may become symptomatic following trauma, due to:

Acute increase in intracystic pressure
Expansion of the cyst
Resultant compression of adjacent brain structures

These changes can lead to neurological symptoms, such as headache, nausea, visual disturbances, or even seizures.

Treatment

Treatment decisions are based on clinical symptoms, cyst size, and location:

Asymptomatic cysts: Regular monitoring with clinical and imaging follow-up.
Symptomatic cysts (as in this case): Surgical options include:
- Endoscopic fenestration of the cyst to communicate with the subarachnoid space.
- Cystoperitoneal shunting in cases of recurrence or persistent enlargement.

Surgical intervention has shown excellent outcomes in most pediatric cases.

References

Al-Holou, W. N., Terman, S., Kilburg, C., Garton, H. J. L., Muraszko, K. M., & Maher, C. O. (2010). Prevalence and natural history of arachnoid cysts in children. Journal of Neurosurgery: Pediatrics, 5(6), 578–585. https://doi.org/10.3171/2010.2.PEDS09357
Helland, C. A., & Wester, K. (2007). A population-based study of intracranial arachnoid cysts: Clinical and neuroimaging findings. Journal of Neurology, Neurosurgery & Psychiatry, 78(10), 1129–1133. https://doi.org/10.1136/jnnp.2006.106435
Wester, K., & Helland, C. A. (2008). Intracranial arachnoid cysts–not always congenital. World Neurosurgery, 69(4), 493–498. https://doi.org/10.1016/j.wneu.2007.10.059
Pérez-Domínguez, M., Gutiérrez, A. M., Escribano, J., & Prieto, R. (2020). Endoscopic management of symptomatic arachnoid cysts in children: Long-term follow-up. Child's Nervous System, 36(1), 151–158. https://doi.org/10.1007/s00381-019-04353-w
Cinalli, G., Spennato, P., Aliberti, F., Trischitta, V., Ruggiero, C., Mirone, G., & Caruso, M. (2006). Endoscopic treatment of arachnoid cysts: A series of 75 pediatric patients. Neurosurgery, 58(4), 765–773. https://doi.org/10.1227/01.NEU.0000209880.15503.B6
Mandonnet, E., Redjimi, M., Parker, F., & Baron, M. H. (2007). Enlargement of arachnoid cyst after minor head trauma. Journal of Clinical Neuroscience, 14(9), 876–879. https://doi.org/10.1016/j.jocn.2006.05.029

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