**History/Background and/or General Information**

Transcranial doppler uses low-frequency doppler transducers applied across the
thin portions of the temporal bone (the temporal acoustic windows) to obtain
flow velocity information from the basal intracerebral arteries. The
transtemporal acoustic window provides access to hemodynamic data from the
middle, anterior, and posterior cerebral arteries. A suboccipital approach,
with insonation through the foramen magnum, provides access to the
intracranial vertebral and basilar arteries, while a transorbital approach can
be used to insonate the ophthalmic artery and the carotid siphon via the optic
foramen. This data allows evaluation of the direction, depth, speed, and
characteristics of flow in these vessels.

**Covered Indications**

Transcranial doppler evaluation of the intracranial cerebrovascular system
will be considered medically necessary in any of the following circumstances:

  * The patient has suspected severe intracranial arterial stenosis based on finite clinical evidence of focal ischemia, and knowledge of this stenosis is necessary in order to properly care for the patient.
  * The patient has areas of known severe stenosis or occlusion of arteries supplying the brain and assessment of the pattern and extent of collateral circulation is necessary in order to properly care for the patient.
  * The patient has suffered a subarachnoid hemorrhage and transcranial doppler studies are necessary to assess vasoconstriction of cerebral vessels.
  * The patient has suspected or confirmed arteriovenous malformation, and an assessment of the arterial supply and flow pattern is necessary.
  * The patient has suspected brain death.

**Limitations**

Headaches or dizziness are not indications for transcranial doppler studies of
the intracranial vessels unless associated with other localizing signs and
symptoms such as nystagmus, limb ataxia, etc.

Transcranial doppler studies performed to monitor cerebral vascular resistance
and the effects of vasodilators and other drugs in the treatment of stroke and
other brain damage is considered investigational, and therefore not covered.

The use of a simple hand-held or other Doppler device that does not produce
hard copy output, or that produces a record that does not permit analysis of
bidirectional vascular flow, is considered part of the physical examination of
the vascular system and is not separately reported. The appropriate assignment
of a specific ultrasound CPT code is not solely determined by the weight,
size, or portability of the equipment, but rather by the extent, quality, and
documentation of the procedure. If an examination is performed with hand-
carried equipment, the quality of the exam, printout, and report must be in
keeping with accepted national standards.

As published in the CMS IOM Publication 100-08, _Medicare Program Integrity
Manual_ , Chapter 13, Section 13.5.4, an item or service may be covered by a
contractor LCD if it is reasonable and necessary under the Social Security Act
Section 1862 (a)(1)(A). Contractors shall determine and describe the
circumstances under which the item or service is considered reasonable and
necessary.