What is the most likely diagnosis for an adult patient with a slow-growing skull lesion, presenting with symptoms such as headaches and visual disturbances, considering their workup?

Most Likely Diagnosis: Meningioma

For an adult patient with a slow-growing skull lesion presenting with headaches and visual disturbances, meningioma is the most likely diagnosis, representing the most common benign skull base tumor in this clinical scenario. 1

Epidemiologic Rationale

• Meningiomas account for the majority of benign primary CNS neoplasms in adults, making them statistically the most probable diagnosis when encountering a slow-growing skull lesion 1
• These tumors characteristically present as slow-growing masses that cause symptoms through mass effect on adjacent structures rather than through invasion 1
• The combination of headaches and visual disturbances is classic for meningiomas affecting the skull base, particularly those in suprasellar or parasellar locations 2, 1

Clinical Presentation Pattern

• Headaches occur commonly with skull base meningiomas and represent one of the most frequent presenting symptoms 2
• Visual disturbances develop when meningiomas compress the optic apparatus, including the optic nerves, chiasm, or tracts, which is particularly common with skull base locations 2
• The slow-growing nature described fits perfectly with meningioma biology, as these tumors typically expand gradually over months to years before becoming symptomatic 1, 3

Alternative Considerations in the Differential

While meningioma is most likely, the differential diagnosis for skull base lesions with these symptoms includes:

• Schwannomas represent 3-5% of skull base tumors but typically present with hearing loss rather than visual symptoms when located in the cerebellopontine angle 2
• Pituitary adenomas should be considered if the lesion is sellar/suprasellar, as they commonly cause visual field defects (bitemporal hemianopsia) and headaches 2
• Skull base leiomyomas/angioleiomyomas are exceedingly rare (only 34 cases reported in literature through 2021) and should be considered only after more common entities are excluded 2
• Chordomas are slow-growing but typically present with cranial nerve deficits and are less common than meningiomas 4

Critical Diagnostic Pitfalls to Avoid

• Do not assume all slow-growing skull lesions are benign—while meningiomas are histologically benign, their location can cause significant morbidity and mortality through compression of vital structures 1
• Do not delay neuroimaging with MRI brain with and without contrast, which is the gold standard for characterizing skull base masses and their relationship to critical neurovascular structures 2, 5
• Do not overlook the need for ophthalmologic examination including formal visual field testing, as visual deficits may be subtle initially but can become irreversible if not addressed promptly 2
• Do not confuse psychiatric symptoms (personality changes, mood disturbances) as primary psychiatric illness—meningiomas can present with isolated neuropsychiatric symptoms, particularly frontal lobe lesions 3

Recommended Diagnostic Approach

• Obtain MRI of the brain with and without contrast as the initial imaging study, which provides superior soft tissue characterization compared to CT and defines the tumor's relationship to adjacent structures 2, 5
• Add thin-section imaging through the skull base if the lesion involves sellar/parasellar regions to better define involvement of the cavernous sinus and optic apparatus 2, 5
• Consider CT of the head with contrast as complementary imaging to evaluate for bone involvement, hyperostosis (characteristic of meningioma), or erosion 2
• Arrange urgent ophthalmologic evaluation with formal visual field testing and fundoscopic examination to document baseline visual function before intervention 2

Management Implications

• Surgical resection remains the primary treatment for symptomatic skull base meningiomas causing mass effect on critical structures 1
• Observation with serial imaging is appropriate for small, asymptomatic meningiomas discovered incidentally, as many remain stable for years 1
• Radiation therapy serves as adjuvant treatment for subtotally resected tumors or as primary therapy for surgically inaccessible lesions 1
• Visual recovery is unlikely after the first postoperative month, making timely surgical intervention critical for preserving vision in cases with progressive visual deficits 5