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Sporadic adult-onset ataxia in a patient with platybasia and basilar invagination

RESUMO

CASE PRESENTATION: A 77-year-old man, white, born in Alagoas, with a negative family history of neurological disease, came to our observation complaining of gait disturbances since 2020. His medical history included systemic arterial hypertension, a depressive disorder and benign prostatic hyperplasia. He reported that his complaints began after a fall from a height in 1982, when he suffered head trauma and that resulted in dizziness with progressive worsening associated with gait imbalance.
Physical examination revealed enlargement of the anteroposterior skull diameter and downbeat nystagmus, ataxia, intention tremor, and wide-based gait. MRI showed evidence of platybasia characterized by a Welcker basal angle of 149.1º. The tip of the odontoid process is located approximately 19 mm from the Chamberlain line, indicating basilar invagination (BI).
DISCUSSION: Platybasia, defined by a Welcher basilar angle greater than 140°, is the flattening of the skull base and may occur as a single finding or in association with other forms of skull base or craniovertebral deformity.
Basilar impression (secondary/acquired) and BI (primary) occur when the mastoid process of C2 invades the foramen magnum and causes compression of the brainstem and upper cervical spine. The top of the mastoid process typically lies below the Chamberlain line (from the hard palate to the opisthion) and is abnormal if it protrudes more than 5 mm above this line.
Platybasia alone does not usually cause symptoms unless it is associated with BI. When it is present, the main symptoms are paraparesis, quadriparesis, ataxia, nystagmus, dysphagia and dyspnea.
The cause of BI is more commonly associated with congenital anomalies such as Klippel-Feil syndrome. Basilar impression is more commonly associated with conditions that cause softening of the bone, including Paget's disease, hyperparathyroidism and osteogenesis imperfecta.
Remarkably, trauma was a precipitating factor for symptoms in patients with BI, as in our patient.
BI is a progressively debilitating disease that can lead to severe neurologic deficits and death if left untreated. Treatment is usually surgical and includes differential decompression followed by posterior stabilization.
FINAL COMMENTS: Our goal is to emphasize the importance of careful clinical observation, in this case, the apparent platybasia and the evaluation of the characteristics of this rare disease, allowing early diagnosis and offering the best possible treatment.

Palavras Chave

platybasia, basilar invagination, ataxia

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