Non-canonical Hedgehog signaling mediates profibrotic hematopoiesis-stroma crosstalk in myeloproliferative neoplasms

The role of hematopoietic Hedgehog signaling in myeloproliferative neoplasms (MPNs) remains incompletely understood despite data suggesting that Hedgehog (Hh) pathway inhibitors have therapeutic activity in patients. We aim to systematically interrogate the role of canonical vs. non-canonical Hh signaling in MPNs. We show that Gli1 protein levels in patient peripheral blood mononuclear cells (PBMCs) mark fibrotic progression and that, in murine MPN models, absence of hematopoietic Gli1, but not Gli2 or Smo, significantly reduces MPN phenotype and fibrosis, indicating that GLI1 in the MPN clone can be activated in a non-canonical fashion. Additionally, we establish that hematopoietic Gli1 has a significant effect on stromal cells, mediated through a druggable MIF-CD74 axis. These data highlight the complex interplay between alterations in the MPN clone and activation of stromal cells and indicate that Gli1 represents a promising therapeutic target in MPNs, particularly that Hh signaling is dispensable for normal hematopoiesis.

Tandem bypass: occipital artery to posterior inferior cerebellar artery side-to-side anastomosis and occipital artery to anterior inferior cerebellar artery end-to-side anastomosis--a case report

A unique example of posterior fossa revascularization is presented. A tandem bypass was performed by anastomosing the midoccipital artery to the posterior inferior cerebellar artery in a side-to-side fashion followed by anastomosis of the distal occipital artery to the anterior inferior cerebellar artery in an end-to-side fashion. The operation was designed to revascularize two separate vascular territories that were isolated in a patient thought to have an extremely compromised posterior circulation. The patient is doing well and is asymptomatic 3 years postoperatively.

Surgical anatomy of the arteries of the posterior fossa

The development of revascularization for vertebrobasilar ischemic events has created a need to identify the best sites at which to perform bypass procedures. Since the occlusive process may selectively affect various levels of the vertebrobasilar tree, sites in different vessels must be used to reestablish flow distal to the area of occlusion. Twenty-seven unfixed human brains were obtained 4 to 8 hours post mortem, and the vertebrobasilar system was injected with polyester resin. Under a surgical microscope the outer diameter, length, and site of origin of major branches were recorded for the following arteries: vertebral, basilar, posterior inferior cerebellar (PICA), anterior inferior cerebellar (AICA), superior cerebellar (SCA), and posterior cerebral (PCA). The ideal sites for an anastomosis were identified as the pretonsillar segment of the PICA, the second portion of the AICA, the perimesencephalic segment of the SCA, and the perimesencephalic part of the PCA. Based on the anatomical observations reported here, these were the best sites because of their outer diameter, degree of mobility, least number of branches, and frequency of occurrence. Use of two of these arteries, however, may pose potential problems: although the PCA has an ideal outer diameter, it also has numerous branches to the brain stem in its most accessible site in the perimesencephalic area; and the PICA is not consistently present, being found in only 75% of the 27 specimens studied.

Acute inflammation and endothelial injury in vein grafts

An experimental study of autogenous vein graft morphology 6 hours after arterial implantation was performed in dogs. The animals were divided into five groups. The first control group had veins harvested and stored but not implanted. The endothelium showed excellent preservation by routine histology and scanning electron microscopy. The second control group had grafts implanted and flow decreased to 30 to 50 ml/minute. There was a massive acute inflammatory response with subendothelial and transmural accumulation of neutrophils causing widespread endothelial sloughing. A third group had grafts implanted, but flow was not reduced (mean, 170 ml/minute). Although an inflammatory response was also present, it was much less severe than in the low flow grafts and the endothelium remained grossly intact. Two other groups had low flow grafts implanted, but were treated with either lidocaine or steroids. Lidocaine had no effect on the inflammatory response or endothelial injury. High doses of alpha-methylprednisolone succinate almost completely prevented both endothelial loss and inflammatory infiltration. This study supports the premise that an acute inflammatory response can initiate endothelial injury after autogenous grafting, an effect that is much more prominent in low flow than high flow grafts. It also demonstrated that steroids can almost totally suppress the injury during the initial 6 hours after implantation.

Vertebrobasilar insufficiency. A review

After critically reviewing the last 50 years' literature pertaining to vertebrobasilar insufficiency, we reached the following conclusions: One can seldom accurately localize vascular pathologic lesions in the posterior circulation by clinical examination alone. The symptoms of vertebrobasilar insufficiency have multiple causes. Stenotic and occlusive lesions have been found at every level of the vertebrobasilar circulation. Currently, a complete investigation requires four-vessel cerebral angiography. No therapeutic modality, medical or surgical, has been proved unequivocably to be of benefit. New surgical approaches to the vertebrobasilar circulation that show promise in providing alternative methods of treatment have been developed.

"Reverse" superficial temporal artery-middle cerebral artery bypass

A new technical variant on the superficial temporal artery-middle cerebral artery anastomosis was performed in a patient with occlusions of both the left internal and external carotid arteries and persistent ischemic symptomatology. Instead of anastomosing the proximal segment of the superficial temporal artery to the middle cerebral artery as is conventionally done, the distal segment of the superficial temporal artery was anastomosed to a cortical branch of the left middle cerebral artery. Reconstituted flow of the left superficial temporal artery via right superficial temporal artery collateral branches proved adequate to relieve the patient's ischemic episodes. "Reverse" superficial temporal artery-middle cerebral artery anastomosis should be considered in those cases where occlusive disease of the external carotid circulation renders conventional bypass procedures ineffective in the treatment of ischemic symptomatology.

Dural arteriovenous malformations and intracranial hemorrhage

Intracranial hemorrhage is seen less frequently with dural than with intraparenchymal arteriovenous malformations (AVMs). We report 6 cases of intracranial hemorrhage among our past 10 patients with dural AVMs. A literature search provided 27 other cases of intracranial hemorrhage from a total of 213 reported dural AVMs. Although hemorrhage was relatively infrequent (7.5%) with dural AVMs located primarily within a major venous sinus, bleeding episodes occurred in 20 of the 39 (51%) cases of malformation outside a major sinus. There was primary leptomeningeal venous drainage in all cases with hemorrhage, and a large variceal dilatation was seen in 14 cases (42%). Dural AVMs located outside a major sinus are uncommon, and they have a propensity for serious intracranial hemorrhage.

The surgical management of vertebrobasilar insufficiency

Vertebrobasilar insufficiency may result from structural lesions anywhere along the vertebrobasilar system. Recently developed techniques in angiography and microsurgery have made the vertebrobasilar system more accessible to surgical therapy. The syndrome of vertebrobasilar insufficiency is discussed, and our experience with the surgical treatment of lesions from the vertebral origin to the distal basilar region is reviewed.

Treatment of a high extracranial carotid artery aneurysm with CCA-MCA bypass and carotid ligation. Case report

✓ This article describes a patient who presented with a developmental aneurysm of the internal carotid artery. Because the aneurysm extended from the carotid bifurcation to the base of the skull, direct arterial reconstruction was precluded. A common carotid artery (CCA) to middle cerebral artery bypass was performed with a saphenous vein graft, followed by gradual occlusion of the distal CCA. The operative technique and a review of the treatment for high cervical carotid aneurysms are presented.

Endarterectomy of the vertebral artery from C2 to posterior inferior cerebellar artery intracranially

A new technical approach to endarterectomy of the vertebral artery at the cranial cervical junction is discussed. A patient had symptoms of vertebrobasilar insufficiency on clinical examination. Angiography demonstrated a stenotic plaque in the vertebral artery at the level of C1, and an additional tandem lesion at the origin of the posterior inferior cerebellar artery. He underwent vertebral endarterectomy and was symptomatically improved postoperatively. The surgical approach used and possible alternatives will be discussed in detail.

Ischemic complications after combined internal carotid artery occlusion and extracranial-intracranial anastomosis

Seven of 120 aneurysm patients admitted to the Henry Ford Hospital from October 1978 to August 1981 had giant internal carotid artery aneurysms that were treated by a combined internal carotid artery occlusion and extracranial-intracranial anastomosis. Three of these patients developed postoperative ischemic complications during the progressive closure of the carotid artery. These complications included the transient onset of syncope, hemiparesis, hemisensory deficits, and dysphasia. These complications resolved after the clamp was reopened and/or intravenous heparin was given. The possible mechanisms involved in the development of ischemia included the development of emboli at the occlusion site or inadequate flow originating from the area of the anastomosis. Prolonged occlusion of the vessel over a 7- to 10-day course with concurrent administration of intravenous heparin is recommended.