From the Guidelines
The workup for a possible osseous skull lesion should begin with a non-contrast CT scan of the head, followed by MRI with and without contrast, as these imaging modalities provide the best characterization of the lesion and its potential impact on surrounding structures. The initial assessment should include a complete history and physical examination, focusing on neurological symptoms, duration of symptoms, and risk factors for malignancy 1. According to the ACR Appropriateness Criteria, when lesions occur in locations with complex osseous anatomy, such as the skull, CT may be a more suitable initial imaging modality 1.
The CT scan provides excellent visualization of bone detail and can characterize the lesion's margins, internal matrix, and effect on surrounding structures. Following the CT scan, an MRI with and without contrast should be performed, as it offers superior soft tissue resolution and can better assess intracranial extension and involvement of adjacent structures. Laboratory studies are also important and should include complete blood count, comprehensive metabolic panel, serum calcium, phosphorus, alkaline phosphatase, and in selected cases, specific tumor markers or hormone levels depending on clinical suspicion.
If the lesion appears potentially malignant or if diagnosis remains uncertain after imaging, a biopsy may be necessary for definitive diagnosis, which can be performed via stereotactic needle biopsy or open surgical biopsy depending on the location and characteristics of the lesion 1. For suspected metastatic disease, additional imaging such as chest/abdomen/pelvis CT, bone scan, or PET-CT may be warranted to identify a primary tumor. The workup should be tailored to the patient's clinical presentation, as skull lesions can range from benign entities like fibrous dysplasia to aggressive malignancies such as metastases or primary bone tumors. Key considerations in the workup include:
- Clinical evaluation and history
- Non-contrast CT scan of the head
- MRI with and without contrast
- Laboratory studies
- Potential biopsy for definitive diagnosis
- Additional imaging for suspected metastatic disease, as necessary.
From the Research
Imaging Modalities for Osseous Skull Lesions
The workup for possible osseous skull lesions typically involves imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI) 2, 3, 4.
- CT is superior to MRI for most osseous lesions and is the modality of choice for evaluating bone destruction or hyperostosis 3, 4.
- MRI provides a complementary role to CT and is useful for detecting skull base lesions, tissue characterization, and assessing neurovascular involvement 3, 4.
Systematic Approach to Diagnosis
A systematic approach to the diagnosis of paediatric skull lesions involves considering clinical-radiological features, imaging characteristics, and differentiating pathologies based on imaging appearances 5.
- This approach highlights the importance of cross-sectional imaging in lesion identification and management implications.
- Accurate diagnosis is paramount, as clinical therapy can vary tremendously depending on the type of lesion.
Common Skull Lesions
Common skull lesions include metastases, multiple myeloma, and eosinophilic granuloma 2.
- Metastases are the most frequent cause of skull lesions and are most commonly due to breast cancer in adults and neuroblastoma in children.
- Multiple myeloma presents as "punched out" lytic lesions on radiographs.
- Eosinophilic granuloma is an osteolytic lesion with bevelled edges.
Importance of Clinical Information
Clinical information, such as the age of the patient and patient history, is fundamental in making the correct diagnosis 2, 3.
- Knowledge of clinical issues and awareness of variants of skull base tumors are essential in making a diagnosis.
- A thorough evaluation of the skull base anatomy and surgical planning using image guidance are crucial for surgeons.