From the Guidelines
Scalloping of the skull vault is primarily caused by conditions that lead to increased intracranial pressure, such as hydrocephalus, intracranial tumors, arachnoid cysts, and idiopathic intracranial hypertension, as well as other conditions like Paget's disease of bone, fibrous dysplasia, hyperparathyroidism, and neurofibromatosis type 1 1. The main conditions that cause this radiographic finding include:
- Hydrocephalus
- Intracranial tumors (especially slow-growing meningiomas, acoustic neuromas, and craniopharyngiomas)
- Arachnoid cysts
- Idiopathic intracranial hypertension Other causes include:
- Paget's disease of bone
- Fibrous dysplasia
- Hyperparathyroidism
- Neurofibromatosis type 1 The mechanism involves chronic pressure against the inner table of the skull, causing bone resorption and the characteristic scalloped appearance on imaging, as bone is a dynamic tissue that responds to persistent pressure by remodeling 1. This occurs because the degree of scalloping often correlates with the duration of increased pressure rather than its severity. In children, whose skulls are more malleable, scalloping may develop more quickly than in adults. When scalloping is identified on imaging, it should prompt a thorough investigation for underlying causes, particularly space-occupying lesions or CSF flow abnormalities, as addressing the primary condition is essential for management. For example, in cases of X-linked hypophosphataemia, brain MRI is recommended to exclude craniosynostosis, Chiari 1 malformation or syringomyelia, especially in symptomatic adults and children with persistent headache, vomiting or abnormal skull shape 1.
From the Research
Conditions that Cause Scalloping of the Skull Vault
- Osteogenesis imperfecta: a rare genetic disorder that leads to progressive skeletal deformities due to deficits in type I collagen, which can cause softening of the bone at the base of the skull, resulting in upward migration of the upper cervical spine and odontoid process into the skull base 2.
- Idiopathic intracranial hypertension: a neurological syndrome characterized by a rise in intracranial pressure without a detectable cause, which can lead to radiological signs such as scalloping of the skull vault 3, 4.
- Increased intracranial pressure: can cause brain herniation and intracranial hypertension, which may lead to scalloping of the skull vault 5.
Associated Factors
- Genetic disorders: such as osteogenesis imperfecta, which can cause skeletal deformities and softening of the bone at the base of the skull 2.
- Obesity: a strong predilection towards obese women of reproductive age, which can contribute to the development of idiopathic intracranial hypertension 3, 4.
- Metabolic and hormonal factors: recent studies have highlighted the pathogenic role of these factors in the development of idiopathic intracranial hypertension 4.