clivo-axial_angle [Neurosurgery Wiki]

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The **clivo-axial angle (CAA)** is a key radiological measurement used to assess the alignment of the craniocervical junction, particularly in the context of conditions like **platybasia** and basilar invagination. 

### Clivo-Axial Angle
- It is the angle formed between the **clivus** (the slope of the skull base) and the axis of the **odontoid process** (C2 vertebra).
- A normal clivo-axial angle is typically between **150° and 165°**.
- A reduced angle (less than 135°) is often associated with abnormalities in the craniocervical junction, such as **brainstem compression** or **cervicomedullary compression**.

### Platybasia
Platybasia is a flattening or abnormal broadening of the skull base. This condition is often linked to:
- A decreased clivo-axial angle.
- Associated with conditions like **Chiari malformation**, **basilar invagination**, and other congenital or acquired craniovertebral junction abnormalities.

### Clinical Implications
- A reduced clivo-axial angle in the context of platybasia can lead to brainstem compression and associated neurological symptoms like **dysphagia**, **dysarthria**, and **upper motor neuron signs**.
- Imaging, including **MRI** and **CT**, is essential for accurately measuring this angle and evaluating the degree of compression.

Assessment of the clivo-axial angle in cases of platybasia is crucial for determining the need for potential surgical interventions like **posterior fossa decompression** or **craniocervical stabilization**.