First Author: C.Florou GREECE
Co Author(s): C. Koutsandrea
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Chiari malformation has, until today, mainly been studied among paediatric populations, usually with a poor visual acuity recovery. The originality of our study consists in the description of an adult patient case showing complete recovery after surgical treatment. Subclinical findings on the brain imaging and the presence of an irrelevant vitreous opacity made the diagnosis more difficult to set. Chiari malformation type I refers to an abnormality of the posterior fossa that has a smaller volume than normal, leading to the herniation of cerebellar tonsils, at least 5 mm below the foramen magnum.
Common symptoms in CMI include headache exacerbated by Valsalva maneuver, ataxia, hydrocephalus. Visual symptoms are present in 80% of patients and include nystagmus, strabismus and diplopia. We describe the case of a 22 year old woman presenting with unilateral sudden visual loss after a self-healing hearing loss days before.
The 22 year old female patient of southeast-Asian origin presented with unilateral, painless, sudden visual loss after a self-healing hearing loss some days before. Ophthalmological examination showed visual acuity of light perception in the left eye, normal ocular motility and an elevated optic disc with indistinct margins and a neighboring vitreous opacity. Pupillary reflex was normal, there was no strabismus, no headache history. Neurological examination showed no acute pathology and brain CT-MRI imaging revealed a small-almost subclinical-herniation of the cerebellar tonsils.The patient was stationary admitted for further investigation.
As investigation eliminated every other infectious or inflammatory cause of a papillitis, neurosurgical intervention was proposed. The patient underwent an uncomplicated occipital craniotomy with posterior fossa decompression and had a favorable revolution with regression of papilledema and a fully recovering visual acuity that reached 10/10.
The occurrence of papilledema associated with Chiari malformation type 1 is rare. Its pathophysiology is explained as a result of raised intracranial pressure and potential direct compression-traction of the nerve roots by cerebral tissue, caudal displacement of the brainstem or vascular disturbance as a consequence of the above. Divergence insufficiency, causing esotropia, can be the initial presentation in patients with minimal cerebellar tonsil herniation, though absent in our case. Differential diagnosis of such cases includes also beginning idiopathic intracranial hypertension as clinical manifestations are similar and impaired intracranial compliance seems to be a common pathophysiological mechanism behind both IIH and CMI. A structural abnormality in the posterior fossa in subjects with type 1 Chiari malformation can lead to malignant increases in cerebrospinal fluid pressure. Such deficit can present with acute onset of visual loss and malignant papilledema, requiring emergent cerebrospinal fluid shunt procedures. Decompressive operations, indicated in such cases, aim to increase the postoperative PCF volume, and specifically the cisterna magna volume, which is associated with a greater likelihood of clinical improvements of headache and tonsillar descent in patients with CM-I.