Sulfhemoglobinemia  is a rare condition in which there is excess sulfhemoglobin (SulfHb) in the blood. The pigment is a greenish derivative of hemoglobin which cannot be converted back to normal, functional hemoglobin. It causes cyanosis even at low blood levels. It is a rare blood condition in which the β-pyrrole ring of the hemoglobin molecule has the ability to bind irreversibly to any substance containing a sulfur atom. When hydrogen sulfide (H2S) (or sulfide ions) and ferrous ions combine in the heme of hemoglobin, the blood is thus incapable of transport oxygen to the tissues. Presentation
Symptoms include a blueish or greenish coloration of the blood (cyanosis), skin, and mucous membranes, even though a blood count test may not show any abnormalities in the blood. This discoloration is caused by greater than 5 grams per cent of deoxyhemoglobin, or 1.5 grams per cent of methemoglobin, or 0.5 grams per cent of sulfhemoglobin, all serious medical abnormalities. Causes
Sulfhemoglobinemia is usually drug induced, with drugs associated with it including sulphonamides, such as sulfasalazine or sumatriptan. Another possible cause is occupational exposure to sulfur compounds.It can also be caused by phenazopyridine. Treatment
The condition generally resolves itself with erythrocyte (red blood cell) turnover, although blood transfusions can be necessary in extreme cases. Notable cases
On June 8, 2007, Canadian anesthesiologists Dr. Stephan Schwarz, Dr. Giuseppe Del Vicario, and Dr. Alana Flexman presented an unusual case in The Lancet.
A newer technology, stacked ABR, may have sensitivity as high as 95% with specificity 88% for smaller tumors. ABR is considerably more cost effective, but MRI provides more information. Stapedius reflex (SR) and caloric vestibular response (CVR) are non-invasive otologic tests for auditory neural function. These are not primary diagnostics for CPA neuromas, and are usually used in conjunction
with ABR. Magnetic resonance imaging
Several different types of magnetic resonance imaging (MRI) may be employed in diagnosis: MRI without contrast, Gd contrast enhanced T1-weighted MRI (GdT1W) or T2-weighted enhanced MRI (T2W or T2*W). Non-contrast enhanced MRI is considerably less expensive than any of the contrast enhanced MRI scans. The gold standard in diagnosis is GdT1W MRI. The reliability of non-contrast enhanced MRI is highly dependent on the sequence of scans, and the experience of the operator. Management
Acoustic neuromas are managed by either surgery, radiation therapy, or observation with regular MRI scanning. With treatment, the likelihood of hearing preservation varies inversely with the size of the tumor; for large tumors, preservation of hearing is rare. Because acoustic neuromas, meningiomas and most other CPA tumors are benign, slow growing or non-growing, and non-invasive, observation is a viable management option. Stereotactic radiosurgery
The objective of irradiation is to halt the growth of the acoustic neuroma tumour, it does not excise it from the body, as the term radiosurgery or gammaknife implies. Radiosurgery is only suitable for small to medium size tumors.