Primary basilar impression

Primary Basilar Impression Primary Basilar Impression is a rare congenital condition characterized by the abnormal positioning of the base of the skull, where the top of the spine (the odontoid process) protrudes into the foramen magnum, the large opening at the base of the skull. This condition can lead to compression of the brainstem and upper spinal cord, resulting in a variety of neurological symptoms.

Etiology

Primary Basilar Impression is considered a congenital anomaly, meaning it is present at birth. It is thought to result from developmental defects during the formation of the skull base and cervical spine. Unlike Secondary Basilar Impression, which is acquired due to other conditions such as Paget's Disease or Rheumatoid Arthritis, primary basilar impression is not caused by external factors or diseases.

Clinical Presentation

Patients with primary basilar impression may present with a range of symptoms, depending on the degree of compression of neural structures. Common symptoms include:

• Headaches
• Neck pain
• Dizziness
• Ataxia (lack of voluntary coordination of muscle movements)
• Dysphagia (difficulty swallowing)
• Visual disturbances
• Hearing loss

In severe cases, patients may experience more serious neurological deficits due to brainstem compression.

Diagnosis

The diagnosis of primary basilar impression is typically made using imaging studies. Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) scans are used to visualize the skull base and cervical spine. These imaging techniques can reveal the abnormal position of the odontoid process and any associated compression of neural structures.

Treatment

Treatment for primary basilar impression depends on the severity of symptoms and the degree of neural compression. Options include:

• Observation: In mild cases with minimal symptoms, regular monitoring may be sufficient.
• Surgical Intervention: In cases with significant neurological symptoms, surgical decompression may be necessary. This can involve removing part of the bone to relieve pressure on the brainstem and spinal cord.
• Symptomatic Treatment: Medications may be used to manage symptoms such as pain and dizziness.

Prognosis

The prognosis for individuals with primary basilar impression varies. Some patients may remain asymptomatic or have mild symptoms throughout their lives, while others may experience progressive neurological decline. Early diagnosis and appropriate management are crucial for improving outcomes.

See Also

• Arnold-Chiari Malformation
• Craniovertebral Junction Anomalies
• Syringomyelia

NIH genetic and rare disease info

• NIH info on Primary basilar impression

Primary basilar impression is a rare disease.