INTRODUCTION:

The term moyamoya comes from a Japanese expression for something "hazy just like a puff of cigarette smoke drifting in the air" was first described by Suzuki and Takaku in 1957.

The disease Moyamoya, which is a Japanese mimetic word, gets its characteristic name due to the appearance of smoke on relevant angiographs resultant from the formed tangle of tiny vessels in response to stenosis to compensate for blockage. An abnormal vascular collateral networks that develop adjacent to the stenotic vessels. This makes the blood leak out of the arteries, causing pressure to the brain and subsequent headaches. The disease primarily affects children, but it can also occur in adults.

Moyamoya disease is an entity that has become more frequently recognized in US as an etiology for Transient Ischemic Attacks and stroke in children, adolescents and young adults and for intra-cerebral haemorrhage in older adult patients.

DEFINITION:

Moyamoya disease is rare, progressive, specific cerebrovascular occlusive disease characterized by stenosis of terminal portion of internal carotid artery and main branches, Circle of Willis. Blood flow is blocked by the constriction and also by blood clots (thrombosis).

Moyamoya disease is a vasculo-occlusive disease involving the circle of Willis, typically the terminal ICA.

Moyamoya disease is a chronic progressive, non-atherosclerotic, non-inflammatory, non-amyloid occlusive intracranial vasculopathy of unknown cause.

Moyamoya disease, which is also known as Moyamoya syndrome, is a rare but very serious condition in which the walls of the internal carotid arteries, the vessels that supply blood to important areas of the brain become thickened and narrowed. This causes the flow of oxygen rich blood to the brain to gradually slow down, and makes it more likely that a blood clot will form.

A collateral circulation develops around the blocked vessels to compensate for the blockage, but the collateral vessels are small, weak, and prone to hemorrhage, aneurysm and thrombosis. On conventional X-ray angiography, these collateral vessels have the appearance of a "puff of smoke" (described as (moyamoya)" in Japanese).

ETIOLOGY:

1. Unknown

2. Inherited genetic abnormalities approx. 10% of cases.Abnormalities on chromosomes 3, 6, 8, and 17 have been linked to familial (inherited) moyamoya disease.

3. Moyamoya can be either congenital or acquired. Patients with Down syndrome, neurofibromatosis type 1, or head trauma can develop moyamoya malformations.

4. Congenital vascular malformations

5. Several diseases are associated with moyamoya-like changes. Although not common, Moyamoya syndrome can occur in patients with neurofibromatosis type I, sickle cell disease, and Down’s syndrome. Moyamoya-like changes can also occur in patients who have undergone radiation or radiotherapy to the head and neck such as in treatment of pituitary tumors and craniopharyngiomas.

Risk factors:

Although the cause of moyamoya disease is unknown, a number of conditions are associated with moyamoya disease:

1. Sickle cell anaemia

2. Cranial radiation

3. Down syndrome

4. Congenital cardiac abnormalities

5. Renal artery stenosis

6. Hyperthyroidism

7. Congenital dwarfism

8. Neurofibromatosis type 1

When a condition like those listed above is associated with moyamoya disease, the disease is called moyamoya syndrome.

INCIDENCES:

- In Japan the overall incidence is higher (0.35 per 100,000) and prevalence is 3.16 cases per 100,000 populations.

- In North America, women in the third or fourth decade of life are most affected.

- In Asia the incidence is 0.28 per 100,000 populations.

- Age distribution in child is 5 to 10 years and in adults the third to fourth decade of life (30- 50 years of age).

- Male / female distribution is 1/1.8 to 1 /2.2.

PATHOPHYSIOLOGY:

- The pathogenesis of moyamoya disease is unknown.

- Once stenosis begins, the process of blockage (vascular occlusion) tends to continue despite any known medical management.

- In some people this leads to repeated strokes and severe functional impairment or even death. In others, this blockage may not cause any symptoms.

^-The disease causes constrictions primarily in the internal carotid artery, and often extends to the middle and anterior cerebral arteries, branches of the internal carotid artery inside the skull.

- When the internal carotid artery becomes completely blocked, the fine collateral circulation that it supplies is obliterated. Patients often survive on the collateral circulation from the back (posterior) of the Circle of Willis, from the basilar artery.

- The constrictions of the arteries in moyamoya disease are unlike the constrictions in atherosclerosis.

- In moyamoya, the inner layer of the carotid artery proliferates within the arterial lumen. The artery also fills with blood clots, which may cause strokes.

- Pathologically, there is fibrocellular intimal thickening and smooth muscle cell proliferation and increased elastin accumulation resulting in stenosis of the intracranial internal carotid arteries. There is also thinning of the media and a tortuous and often multilayered internal elastic lamina.

The progression of Moyamoya follows a typical course and can be classified into stages based on angiography findings:

Stage I: Narrowing of internal carotid arteries

Stage II: Development of moyamoya vessels at the base of the brain

Stage III: Intensification of moyamoya vessels and internal carotid artery narrowing (most cases diagnosed at this stage)

Stage IV: Minimization of moyamoya vessels and increased collateral vessels from the scalp

Stage V: Reduction of moyamoya vessels and significant internal carotid artery narrowing

Stage VI: Disappearance of moyamoya vessels, complete blockage of internal carotid arteries, and significant collateral vessels from the scalp

Once the process of blockage (vascular occlusion) begins, it tends to continue. No known medication can reverse the blockage. Once a major stroke or bleeding has occurred, the patient may be left with permanent loss of function. It is important, therefore, to treat this condition promptly.

CLINICAL MANIFESTATIONS:

1. In children- stroke or epilepsy

2. In adult – it tends to cause stroke and bleeding

3. Transient ischemic attack – often precipitated by crying, blowing or hyperventilation.

4. Ischemic stroke

5. Hemorrhagic stroke

6. Convulsion or Epilepsy

7. Sensorimotor paralysis (numbness and paralysis of the extremities)

8. Migraine like headache

9. Disturbed consciousness

10. Speech deficits (usually aphasia)

11. Sensory and cognitive impairments

12. Involuntary movements

13. Altered vision

14. Mental deterioration

15. Learning disabilities

DIAGNOSTIC TESTS:

- CT scan: Provide more details about head injuries, tumors and brain diseases.

- Computed Tomography Angiography (CTA) scan is a non-invasive X-ray that provides detailed images of anatomical structures within the brain.

- Computed Tomography (CT) Perfusion imaging is a noninvasive test that detects blood flow in the brain and is used in planning surgery.

- MRI: It visualizes changes in narrowing of vessels of circle Willis and areas of previous stroke. More sensitive than CT, with use of diffusion and perfusion. Allows identification of early ischemic areas.

- An MRA (Magnetic Resonance Angiogram): is performed during an MRI by injecting a contrast agent into the blood stream so that arteries of the brain can be seen.

- Nuclear medicine studies such as SPECT (single photon emission computerized tomography) are used to demonstrate the decreased blood and oxygen supply to areas of the brain involved with moyamoya disease.

- Conventional angiography provided the conclusive diagnosis of moyamoya disease. Small abnormal net-like vessels proliferate giving the characteristic "puff of smoke" appearance on direct angiography. Aneurysms or arteriovenous malformations (AVMs), known to be associated with moyamoya, can also be detected.

- Cerebral blood flow studies, such as transcranial Doppler ultrasonography (TCD), xenon-enhanced CT, positron emission tomography (PET), and single photon emission computed tomography (SPECT), also can help with their diagnosis and treatment of patients with moyamoya.

ASSOCIATED DISEASES:

Although moyamoya disease may occur by itself in a previously healthy individual, many disease states have been reported in association with moyamoya disease, including the following:

· Immunologic –Grave’s disease/ thyrotoxicosis

· Infections - Leptospirosis and tuberculosis, basilar and tubercular meningitis

· Hematologic disorders - Aplastic anemia, Fanconi anemia, sickle cell anemia, and lupus anticoagulant, thalassesmia

· Congenital syndromes - Down syndrome, Marfan syndrome, tuberous sclerosis, Turner syndrome, von Recklinghausen disease (Neurofibromatosis Type 1), and Hirschsprung disease, William’s syndrome

· Vascular diseases - Atherosclerotic disease, coarctation of the aorta and fibromuscular dysplasia, cranial trauma, radiation injury, and hypertension.

· Certain human leukocyte antigen (HLA) types favours a hereditary basis

· Neonatal anoxia

· Brain tumors

· Oral contraceptives

· Renal artery stenosis

· Factor XII deficiency

· Pulmonary sarcoidosis

These associated conditions may not be causative, but they do warrant consideration due to their impact on treatment. In the presence of these risk factors, the condition is referred to as moyamoya syndrome.

MANAGEMENT:

MEDICAL MANAGEMENT:

Medical management of moyamoya disease includes the following:

1. Maintenance of hydration

2. Use of antiplatelet agents like aspirin or Plavix (clopidogrel bisulfate)

3. Moderate control of hypertension

- No medication can stop or reverse the progression of moyamoya disease. Treatment focuses on reducing the risk of stroke and restoring blood flow to the brain.

- Symptomatic and directed towards reducing elevated intracranial pressure, improving cerebral blood flow and controlling seizures.

- Drugs such as antiplatelet agents (including aspirin) are usually given to prevent clots, but surgery is usually recommended.

- If intracerebral haemorrhage has occurred, then management of hypertension (if present) is imperative. In cases of severe stroke, intensive care unit (ICU) monitoring is indicated until the patient's condition stabilizes. If the patient has had an ischemic stroke, consider anticoagulation or antiplatelet agents.The rationale behind the administration of anticoagulation and antiplatelet agents is the prevention of further strokes, especially in stenotic vessels.

SURGICAL MANAGEMENT:

1. Direct revascularization: superficial temporal artery and middle cerebral artery anastomosis is considered the treatment of choice, although its efficacy, particularly for hemorrhagic disease, remains uncertain. This procedure is also commonly referred to as an EC-IC (External Carotid-Internal Carotid) bypass.

It reduces the risk of haemorrhage thus results in important clinical improvement as well as has reduced the risk of haemorrhage because the new collateral circulation into the larger conduit arteries of the brain reduces the stimulus for developing new collateral circulation.

2. Indirect revascularization:

a. Multiple burr holes have been used in frontal and parietal lobes with good neovascularisation achieved. Multiple small holes (burr holes) are placed in the skull to allow for growth of new vessels into the brain from the scalp.

b. EDAS: The EDAS (encephalo-duro-arterio-synangiosis) procedure is a synangiosis procedure that requires dissection of a scalp artery over a course of several inches and then making a small temporary opening in the skull directly beneath the artery. The artery is then sutured to a branch of the middle cerebral artery on the surface of the brain and the bone replaced. It is the treatment of choice in pediatric patients as their vessels are too small to allow direct anastomosis.

c. EMS:In the EMS (encephalo-myo-synangiosis) procedure, the temporalis muscle, which is in the temple region of the forehead, is dissected and through an opening in the skull placed onto the surface of the brain.

d. ECA- MCA: external carotid artery to middle cerebral artery anastomoses can be performed as the vessels are larger.

e. EDAMS (encephalo-duro-arterio-myo-synangiosis) procedure is an indirect method of revascularization. It combines the technique of EDAS and EMS.

f. Omental transposition procedure is an indirect method of revascularization in which the omentum (the lining surrounding the abdominal organs), which is very rich in blood supply, is placed on the surface of the brain, with the expectation that vessels will eventually grow into the brain and improve blood supply.

g. Pial synangiosis that directly affixes a healthy donor artery to the affected area of a patient’s brain.

PROGNOSIS:

The long term outlook for patients with treated moyamoya seems to be good. While symptoms may seem to improve almost immediately after the in-direct EDAS, EMS, and multiple burr holes surgeries, it will take probably 6–12 months before new vessels can develop to give a sufficient blood supply. With the direct STA-MCA surgery, increased blood supply is immediate.

If a patient is surgically treated prior to a disabling stroke, even if the condition is severe, the prognosis tends to be excellent. Even in patients without symptoms, surgical treatment has been reported to protect against stroke. However, if left untreated, the disease will invariably progress, producing clinical deterioration and potentially irreversible neurological deficits over time. Without treatment, Moyamoya disease can be fatal as the result of intracerebral haemorrhage.

For patients who have long-term damage from strokes, treatment will also focus on physical therapy, speech therapy, and occupational therapy to help them regain function and cope with any remaining disability.

Mortality rates from moyamoya disease are approximately 10% in adults and 4.3% in children.

Rehabilitation:

Rehabilitation with physical therapy, occupational therapy, and speech therapy should be considered, depending on the neurologic impairment. The extent of therapy can range from bedside treatment to full, comprehensive inpatient rehabilitation. The latter would include physical, occupational, speech, and cognitive therapy.

A Case of Moyamoya disease admitted in one of the City Hospital at Pune:

My client XYZ, 28yrs. Old, admitted in one of the city hospital at Pune. He came to hospital with complaints of severe headache with sudden onset, neck pain followed by loss of consciousness. He is a known case of moyamoya disease with subarachnoid haemorrhage.

He had same complaints on 11/10/2014. So he got admitted in Ahmadnagar Hospital which is near to patient’s house. After doing CT scan it showed intraventricular haemorrhage involving bilateral, 3^rd and 4^th ventricle secondary to aneurysm or AVM. Blood at bilateral, lateral ventricle having thick cast producing hydrocephalus.

He underwent external ventricular drain placement. When CT scan done thereafter it showed acute hematoma in bilateral frontal pericallosal region. It is causing mass effect on the underlying brain parynchyma and ventricles. There is intraventricular extension of the bleed with mild dilation, diffuse cerebral edema.

Then patient referred to one of the city hospital at Pune on 25/10/2014 with quadriplegia. Cerebral Digital Subtraction Angiography (DSA) test was done. It showed that chronic total arterial occlusion of left ICA beyond ophthalmic segment. Reformation of left MCA and ACA from left PCA and right ACA via tortuous tiny moyamoya like vessels.

Plain CT brain done it showed acute and subacute infarct involving left thalamus and adjacent gangliocapsular region with its mass effect. Minimal residual intraventricular haemorrhage.

He was getting diuretics, antiepileptics, analgesics as medical management. After postoperative care patient was discharged and returned for follow up after few weeks. Patient condition was satisfactory.

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Received on 04.03.2016 Modified on 06.04.2016

Int. J. Nur. Edu. and Research. 2017; 5(2): 218-222.

DOI: 10.5958/2454-2660.2017.00047.3