The National Institute for Health and Clinical Excellence (NICE) has issued full guidance to the NHS in England, Wales, Scotland and Northern Ireland on Extracranial to intracranial bypass for intracranial atherosclerosis.

It replaces the previous guidance on High-flow interposition extracranial to intracranial bypass (NICE interventional procedures guidance 73, July 2004).


In intracranial atherosclerosis disease, blood vessels (arteries) in the head can become narrowed or blocked. An extracranial to intracranial bypass is an operation to join a blood vessel outside the skull to one inside the skull, bypassing the problem. The aim is to maintain and improve blood supply to the brain to prevent stroke.

Coding recommendations

L29.6 High-flow interposition extracranial to intracranial bypass from external carotid artery to middle cerebral artery


L29.7 Bypass of carotid artery by anastomosis of superficial temporal artery to middle cerebral artery


L29.8 Other specified reconstruction of carotid artery

Note: L29.8 is used to capture all other extracranial to intracranial bypass procedures not included at L29.6 or L29.7. Additional codes are required if a graft is utilised.

Your responsibility

This guidance represents the view of NICE, arrived at after careful consideration of the evidence available. When exercising their judgement, healthcare professionals are expected to take this guidance fully into account. However, the guidance does not override the individual responsibility of healthcare professionals to make decisions appropriate to the circumstances of the individual patient, in consultation with the patient and/or guardian or carer.

Commissioners and/or providers have a responsibility to implement the guidance, in their local context, in light of their duties to have due regard to the need to eliminate unlawful discrimination, advance equality of opportunity, and foster good relations. Nothing in this guidance should be interpreted in a way that would be inconsistent with compliance with those duties.

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