What is Moya Moya disease?

Moyamoya disease (MMD) is a chronic cerebro vascular disease characterized by progressive arterial stenosis or occlusion of bilateral intracranial carotid arteries (ICA) and the development of extensive collateral vessels usually at the base of the brain.

First described in 1957 as "hypoplasia of bilateral internal carotid arteries," the descriptive title of "moyamoya" – puff of smoke was coined more than a decade later by Suzuki and Takaku.

Moya Moya disease spectrum can be divided into Moya Moya syndrome (MMS) or quasi-Moya Moya (those with a well-recognized associated condition and angiographic evidence of uni/bilateral stenosis) and moyamoya disease (MMD, those without any associated disorder and bilateral stenosis)

Gradual reduction of cerebral blood flow stimulates collateral vessel formation, with characteristic "moyamoya" blush seen on angiography.

Though MMD occurs in a worldwide distribution, it is more common in Japan and Korea, with the incidence estimates of 0.35-0.54/100,000 population. In India MMD is common in Northeast India.

How is it diagnosed?

The classical presentations of MMD include transient ischemic attacks (TIAs), ischemic strokes, and intracranial hemorrhages. However it can present with a various transient neurological symptoms, frequently overlooked, leading to delayed diagnosis, and contributing to socio-economic burden, especially in India.

CT scan is preliminary investigation for patients with hemorrhagic stroke. MRI with MRA and MRV is another primary modality of investigation, which shows most commonly border zone infarct followed by gyral pattern in children and subcortical infarcts in adults. However a quarter of MRI will be normal in symptomatic patients. Angiography was the gold standard for confirmation of diagnosis. Angiogram is must for treatment planning and further follow ups.

Is it common in children? If so Why?

MMD is a rare and uncommon disease in any age group. As per literature available it is more common in children. It has bimodal distribution, majority seen in 3-8 years followed by a next peak at 41-47 years. It accounts for 6% of childhood strokes. Any child can have Moya Moya, however commonly seen in children of Asian descent with unknown cause.

Sometimes it is associated with

  • Down syndrome
  • Neurofibromatosis
  • Sickle cell disease
  • History of head or neck radiation

How common is it in India and what is the cause?

It is uncommon in India. The exact incidence of MMD in India is unknown as there is no national registry for this rare disease at present. In our country there is often delay in identifying MMD spectrum as these patients can present with various neurological symptoms. This has huge burden with impact on the socio-economic front with high disability.

The exact cause of MMD is still unknown. However there may be genetic and familial factors involved in the disease formation and progression . Here at APCC high-risk cases are managed in a specialised tertiary centre with excellent facilities. The advanced surgical techniques and availability of technology in combination with expertise improves the chances of saving a patient’s life even in critical complications.

What was unique in this case of Moyamoya?

The first case to be witnessed in Asia of Moya Moya disease—a rare blood vessel (vascular) disorder in which the carotid artery in the skull is blocked or narrowed—reduces blood flow to the brain. The condition was diagnosed in eight-year-old twin girls. MRI scan of the brain showed that the blood supply to the brain was significantly compromised on both sides of the brain, especially on the left. These episodes originally thought to be as seizures were a form of multiple mini-strokes often called limb-shaking epilepsy, which signifies compromised blood circulation to the brain.

How was it treated at APCC and what was the outcome?

Direct revascularization by STA-MCA bypass provides the benefit of both immediate and progressive revascularization and the anastamosis is proven to enlarge up to 50% with time. Indirect revascularization method like EDAMS also has proven benefits. However many studies point to better long term outcome when both Direct and Indirect revascularization methods are combined.

While surgery is the only viable treatment for moyamoya disease in the long term, patients also need medication to manage the interim which may include ASPIRIN (for blood thinning) or VERAMPAMIL (Calcium channel blocker) to reduce blood pressure.

We reviewed the twin siblings one week after discharge for wound inspection which had healed well. They did not experience any new symptoms of stroke or epilepsy. Repeat MRI brain perfusion studies performed in both of them after one month showed good perfusion on the left side. Presently, they had gone abroad along with their parents and we would review them after a year. They may need bypass on the right side as well based on the follow up imaging studies.

Out of the two twins one was more affected than the other though seizures were present in both twin siblings. As Moya Moya disease is usually bilateral, we did acetazolamide challenged MRI brain perfusion studies to identify the side more affected. Accordingly, we planned to perform the cerebral bypass (STA-MCA) on the more symptomatic sibling on left side on one day and the other sibling the next day. The surgery lasted for 5 hrs in each and the challenge was performing the bypass in extremely small caliber vessels less than 1 mm. However, the result was was more than expected and we could do the bypass successfully and confirmed by intra operative ICG dye angiography. In addition to the bypass, we also performed indirect revascularization (EDAMS) for better long term outcome. Both the twin siblings recovered well from the procedure and were discharged 5 days after the surgery.