Cryptococcus gattii CNS infection presenting as a periaqueductal "soap-bubble" lesion causing obstructive hydrocephalus with refractory CSF diversion.

Cryptococcosis is a potentially systemic fungal infection that may present in both immunocompetent and immunocompromised individuals, of which Cryptococcus gattii is the rarer cause. The most severe form of cryptococcosis involves the CNS. We present a case of C. gattii infection of the CNS in a 63-year-old male presenting to the emergency department mainly for a ground level fall, declining physical and mental activity, and constitutional symptoms. Initial workup revealed sinus bradycardia, hypertension, moderate hyponatremia, and malnutritional immunocompromise. The initial brain MRI with and without contrast showed a 2.1 × 1.6 × 1.4 cm complex, multicystic, necrotic, heterogeneously enhancing lesion ("soap-bubble" appearance) occupying the left posteromedial thalamus, tectum, and periaqueductal region slightly crossing the midline with dilation of the lateral and third ventricles. Management for stroke concern was conducted, VP shunt was placed, and C. gattii was found in samples from bronchoscopy and lumbar puncture. Antifungal therapy was started, but worsening findings on repeat neuroimaging required intensive care and external ventricular drain placement with unchanged subsequent imaging findings. Despite intravenous steroids for intracranial edema and prophylaxis for seizures, the patient progressively declined overall. Ultimately, prognosis was guarded, leading to discharge with hospice care. On a whole, this case captures notable imaging characteristics of C. gattii CNS infection involving invasive interventions, which very few cases have accomplished thus far. Particularly, it highlights the phenomenon of a "soap-bubble" lesion causing obstructive hydrocephalus, which is uncommon.