Tag: carotid endarterectomy

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Carotid techniques

Brain Claudication -is it a thing?

CTA tends to overread stenoses which was in the 60-79% range on duplex

The patient is a middle aged executive who complains of bouts of aphasia triggered by intense conversations and business meetings. It first occurred while driving to Dubai on a conference call. Since then, they occurred several times a week, typically triggered during meetings where he needs to think and speak. Casual conversation and cognition does not seem to trigger this. Workup revealed a heterogeneous plaque affecting the left ICA with velocities in the 60-79% range. CTA confirmed this plaque. MRI failed to show any stroke or other lesions. Neurology evaluation showed normal exam. The patient underwent endarterectomy, and had a normal recovery. In followup, he denied any further episodes of aphasia.

Standard endarterectomy with patch

Aphasia, the loss of function in the language centers, typically of the left brain, although in a minority, it may live in the right hemisphere, is terrifying manifestation of stroke. This case, if examined superficially, is nothing special in that TIA’s associated with a reasonable culprit lesion went away after elimination of that culprit lesion. To me, it was fascinating because it represents a possible case of brain claudication.

The human brain is believed to have evolved to its large size in conjunction with bipedalism, social hunting and gathering, and climate change in the Great Rift Valley favoring a savannah over forests, that created heat stresses on the brain, favoring the development of sweating and redundancies in brain tissue. The advent of fire and cooking enhanced available calories to feed this enlarged brain’s metabolic needs. When the metabolism isn’t supported through adequate blood supply, the brain tissue dies. Rarely, it blinkers on and off, and even more rarely, this occurs in the motor strip triggering today a neurologic evaluation including a carotid duplex that brings these patients to our attention. The fascinating question for me is, does increased metabolic demand in the form of complex thinking result in a supply-demand mismatch much as seen in exercise induced angina or claudication? If it can, can we test for it?

The tests we have available are hemodynamically based. At its simplest, after carotid angiography, an occluding balloon can be inflated to test for symptoms. This is an archaic test and I do not do it. There are nuclear medicine, PET CT, and MRI tests that use pharmacologic agents to induce hypotension, but again, for this patient, it wouldn’t apply. This patient needed the equivalent of a treadmill in the MRI machine. Maybe having him read a dry, technical treatise on neurobiology taped to the MRI tube?

I went to the OR with the indication of TIAs associated with a >50% lesion, but I did tell the patient that it was possible his thinking-induced aphasia would not remit. Thankfully it did.

Categories
Carotid

Oblique Incisions Do Not Compromise Exposure During Carotid Endarterectomy

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I was asked to assist one of my otolaryngology colleagues in extirpating a neck tumor that encroached on the carotid artery at the base of the skull early in my career. While the operation was complex and interesting, the most impressive part of it was the complete exposure of the neck from base of skull to the base of neck that was possible with an oblique skin line incision. This challenged bias I had about “exposure,” because up to that time, I had done the mastoid process to manubrium incision along the anterior border of the sternocleidomastoid muscle. What was doubly remarkable was that the incision was invisible in followup despite curling from ear to epiglottis because it was hidden in the fold under the submandibular fat.

This patient above had his carotid endarterectomy performed with a skin line incision. He didn’t even need his beard shaved for the operation.

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The key is developing subplatysmal flaps like the kind you make with thyroidectomy. This allows cephalad and caudad exposure. More exposure means just extending the incision medially and laterally. These flaps heal well. This with retraction allows for excellent exposure of the neck.

OR

plaque

The other advantage is that the fat is never cut across but completely avoided if you go under it and lift it up. The incision is far less disfiguring and heals well because the forces co-apt the skin without relying on tension from the closing sutures. Preop planning with CTA and 3D virtual reconstruction confirm where the incision should be placed. But most of all, the patients appreciate not having a scar on the neck that they have to constantly explain.

Planning starts with visualizing the proximal and distal extend of plaque needed to be removed.

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The 3D reconstruction view can be “Window Level”-ed to bring in soft tissues and skin to anticipate the operative exposure.

planning

Experience has shown me that it is possible to avoid cutting through the fat on the neck, and what is visually the lower part of the face as much as it is the neck, but performing this oblique incision in the skin fold.

incision

Categories
Carotid techniques

The carotid baroreptor -can it be reconstituted after carotid endarterectomy?

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While I was a site investigator for the CVRx Rheos Trial, a device that induced hypotension and bradycardia by stimulating the carotid baroreceptor with electrical energy to control resistant hypertension, I noticed that Hering’s nerve can be readily identified by accompanying arteries which show up as paired red lines. The baroreceptor complex is a pressure transducer and the maximum dP/dt can be transduced in areas of maximum curvature change. If you recall those tension maps of aneurysm rupture points, they occur in areas of maximum curvature and inflection points -wouldn’t a baroreceptor be constructed to sense pressure and change in pressure here? Hering’s nerve comes out over these areas. It struck me that most of the patients with carotid disease are hypertensive and it may be a disease cycle that occurs with stiffening of the baroreceptor, decreased parasympathetic tone, and hypertension as the output signal with subsequent vessel injury and plaque formation and worsening stiffness -a non virtuous cycle.

The nerve probably wraps around the origin of the internal carotid artery or wherever the curvature is best suited for pressure transduction. If you visualize the bulbous origin of the ICA as the belly of the guppy, the arteriotomy is made traditionally on the side facing you which is on the side and across at least half of Hering’s nerve -on the lateral surface of the guppy. If you make instead an arteriotomy on the belly of the guppy, and preserve as much of these nerves as possible, it would be theoretically possible to reconstitute a baroreceptor, maybe the dominant one (there is a sidedness to the baroreceptor strength).

There is an intriguing consequence to cutting the nerves -for example in skeletonizing the ICA for an eversion. Eversion endarterectomy done this way is associated with greater incidence of postop hypertension than standard endarterectomy (ref 1,2). The question is if the converse -if reconstituting the baroreceptor can bring decreased need for anti hypertensive medications or even hypotension and bradycardia -is true and if there is potential for applying this as therapy for hypertension as well as stroke risk reduction.

References
1. J Vasc Surg. 2012 Aug;56(2):324-33.
2. J Vasc Surg. 2001 Nov;34(5):839-45.