Phd Graduate Investigates Vision Loss in Cryptococcal Meningitis Patients
A study by Dr Anand Moodley, Head of Neurology at Greys Hospital in Pietermaritzburg, examined the causes of vision loss through fungal infection of the brain and spine.
Moodley graduated with a PhD in Neurology from UKZN’s College of Health Sciences on 10th April with a thesis titled: “A Qualitative and Quantitative (MR) Diffusion Study Investigating the Pathogenesis of Cryptococcal Induced Vision Loss”.
Cryptococcal meningitis (CM), which causes vision loss through a fungal infection of the tissues that cover the brain and the spine, is an opportunistic infection found in HIV infected patients. Vision loss occurs in 35-48% of patients.
With conflicting reports concerning the cause of visual loss in CM, various authors have supported an optic neuritis (inflammation) model while others have preferred a papilloedema (raised intracranial pressure) model. Due to these conflicting models, effective strategies for prevention and treatment of visual loss in CM have been delayed.
The aim of Moodley’s study was to clarify the cause of cryptococcal-induced visual loss by using diffusion imaging of the optic nerve as an investigational tool. Diffusion imaging is a magnetic imaging technique which derives images based on diffusion on water in various tissues.
The study investigated 95 patients with CM and showed that optic neuritis (inflammation of the optic nerve) is uncommon, while papilloedema (swelling caused by intracranial pressure) occurs in 25% of patients, yet raised pressure was present in 71% of patients.
By using optic nerve diffusion imaging, Moodley was able to show that raised intracranial pressure played the primary role in CM induced visual loss. The raised pressure was more likely to cause an optic nerve compartment syndrome at the optic canal level rather than papilloedema as the main insult resulting in visual loss.
‘Optic nerve diffusion imaging has become a useful tool in investigating the micro-structure of optic nerve function,’ said Moodley. ‘Its applications have been mostly to optic neuritis and ischaemic optic neuropathy. This is the first time it has been applied to an infectious disease. The technique was reliable and reproducible and produced diffusion parameters equivalent to other investigators in the field.’
Moodley’s current focus is the supervision of MMED students and further development of neuro-ophthalmology. In his spare time, he enjoys golf, squash, birding and… Mathematics!
- Zakia Jeewa