The original ultrasound-guided technique for injection of the GON was described by Greher and colleagues in 2010; it targets the nerve as it courses superficial to the obliquus capitis inferior muscle at the C1-C2 level.There are several advanced interventional procedures in clinical use:
Pulsed or thermal radiofrequency ablation (RFA) may be considered for longer-lasting relief after a local anesthetic blockade confirms the diagnosis. Thermal RFA aimed at destroying the nerve architecture can render long-term analgesia but also comes with the potential risks of hypesthesia, dysesthesia, anesthesia dolorosa, and painful neuroma formation. Chemical neurolysis with alcohol or phenol carries the same risks as thermal RFA. There is no such risk with pulsed RF, however, some question its efficacy as compared to other procedures. Neuromodulation of the occipital nerve(s) involves the placement of nerve stimulator leads in a horizontal or oblique orientation at the base of the skull across where the greater occipital nerve emerges. Patients should be trialed with temporary leads first, and greater than 50% pain relief for several days is considered a successful trial after which permanent implantation may be considered. Risks include surgical site infection and lead or generator displacement or fracture after the operation. Ultrasound-guided percutaneous cryoablation of the GON is sometimes performed. At the correct temperature, there should be stunning but not permanent damage of the nerve, but at temperatures below negative 70 degrees Celsius, nerve injury is possible.
Purtschers retinopathy is a disease where part of the eye (retina) is damaged. Usually associated with severe head injuries, it may also occur with other types of trauma, such as long bone fractures, or with several non-traumatic systemic diseases. However, the exact cause of the disease is not well understood. There are no treatments specific for Purtschers retinopathy, and the prognosis varies. The disease can threaten vision, sometimes causing temporary or permanent blindness. It is named for the Austrian ophthalmologist, Othmar Purtscher (1852–1927), who detected it in 1910 and described it fully in 1912. Presentation
Associated diseases
Severe head, chest, or long bone trauma
Acute pancreatitis
Amniotic fluid embolism
Chronic kidney failure
Dermatomyositis
Fat embolism syndrome
Scleroderma
Systemic lupus erythematosus (SLE)
Thrombotic thrombocytopenic purpura (TTP)

Pathophysiology
Purtschers retinopathy likely involves complex pathophysiology, with several contributing factors, including complement-mediated aggregates, fat, air, fibrin clots and platelet clumps. The diseases leads to the formation of cotton wool spots in the retina, a finding observed in several other diseases, and atrophy of the optic nerve. Diagnosis
Where trauma is involved, only a funduscopic examination of the back of the eye (retina) is necessary to make the diagnosis. Fluoroscein angiography may show a decrease in blood flow to the areas of whiteness in the retina. Treatment
It may be treated with triamcinolone in some cases. However, in general, there are no treatments for Purtschers retinopathy. If it is caused by a systemic disease or emboli, then those conditions should be treated. Prognosis
Purtschers retinopathy can lead to loss of vision, and recovery of vision may occur very little.