Bilateral putaminal necrosis and bronopol toxicity

Abstract

Among alcohols, methanol intoxication is the most frequently associated with cerebral toxicity, causing retinal damage and putaminal necrosis. This consequence is believed to be due to the transformation of methanol into formic acid. We describe the case of a patient who presented with acute impairment of consciousness and tetraparesis after she had been drinking several bottles of a topical antiseptic solution (Lysoform Medical) containing 2-bromo-2-nitro-1,3-propandiol (bronopol) among excipients, in order to lose weight during previous months. Moreover, she had been on a strict slimming diet. Soon after admission, a severe respiratory and metabolic impairment became rapidly evident, requiring an intensive care unit admission. Cerebral MRI showed the presence of bilateral putaminal necrosis. She recovered in 10 days, surprisingly, without any evident clinical neurological signs. Methanol, also bronopol, when diluted in aqueous solution, at warm temperature and/or higher pH, may release formaldehyde, which is converted into formic acid, a basal ganglia toxic compound.

Figure 1

(A–D) Brain MRI performed on the second day after admission. Axial T2-weighted images showing a symmetrical bilateral hyperintensity of the putamen, extending also to external capsule and corona radiata (A and B). The gradient echo T2-weighted image showing the presence of haemosiderin inside the lesions as haemorrhagic necrosis (C). Optic nerves have a normal appearance (D). (E–H) Brain MRI performed on the 20th day after admission. T2-weighted images showing a slight reduction in size of bilateral hyperintensity of the putamen (E and F). The amount of haemosiderin inside the lesions is reduced (G). No abnormalities of the optical nerves are detected (H).

Figure 2

In aqueous solutions, bronopol rapidly degrades to various transformation products, consisting of 2-bromo-2-nitroethanol, bromonitromethane and formaldehyde. Formaldehyde is then rapidly metabolised into formic acid, largely in the liver, by the catalytic action of formaldehyde dehydrogenase; this conversion has an estimated half life of 1.5 min. Modified from Cui et al.