Historically cyanide has been used for mass suicide and by the Nazis for genocide. Signs and symptoms
Acute exposure
If hydrogen cyanide is inhaled it can cause a coma with seizures, apnea, and cardiac arrest, with death following in a matter of seconds. At lower doses, loss of consciousness may be preceded by general weakness, dizziness, headaches, vertigo, confusion, and perceived difficulty in breathing. At the first stages of unconsciousness, breathing is often sufficient or even rapid, although the state of the person progresses towards a deep coma, sometimes accompanied by pulmonary edema, and finally cardiac arrest. A cherry red skin color that darkens may be present as the result of increased venous hemoglobin oxygen saturation. Despite the similar name, cyanide does not directly cause cyanosis. A fatal dose for humans can be as low as 1.5 mg/kg body weight. Other sources claim a lethal dose is 1–3 mg per kg body weight for vertebrates. Chronic exposure
Exposure to lower levels of cyanide over a long period (e.g., after use of improperly processed cassava roots, which are a primary food source in tropical Africa) results in increased blood cyanide levels, which can result in weakness and a variety of symptoms, including permanent paralysis, nervous lesions, hypothyroidism, and miscarriages. Other effects include mild liver and kidney damage. Causes
Cyanide poisoning can result from the ingestion of cyanide salts; imbibing pure liquid prussic acid; skin absorption of prussic acid; intravenous infusion of nitroprusside for hypertensive crisis; or the inhalation of hydrogen cyanide gas.
On the other hand, the fronto-supraorbital advancement and remodelling and the floating forehead technique create sufficient space for brain growth and result in a normal horizontal axis of the orbits and supraorbital bar. The fronto-supraorbital advancement and remodelling is the most used method nowadays. Over the past few years distraction osteogenesis has been gradually acknowledged since it has a positive effect on hypotelorism. Expanding the distance between the orbits using springs seems to be successful. However, there are discussions whether hypotelorism really needs to be corrected. The minimal invasive endoscopic surgery has been gaining attention since the early 90s, however, it has technical limitations (only strip craniectomy is possible). Attempts have been made to reach beyond these limits. Aesthetic
Aesthetic outcome of metopic  synostosis surgery is persistently good with reoperation hazards below 20%. In 1981 Anderson advised that craniofacial operations for synostosis should be as extensive as necessary after a study of 107 cases of metopic and coronal synostosis. Surgery does not provide a 100% natural outcome, mostly there will be minor irregularities. Reoperations are usually performed on more severe cases (including syndromic metopic synostosis). The hypotelorism  and temporal hollowing are the most difficult to correct: the hypotelorism usually remains under corrected and a second operation is often needed for correction of temporal hollowing. Neurological
The highest rate of neurological problems of single suture synostosis are seen in patients with trigonocephaly. Surgery is performed generally before the age of one because of claims of better intellectual outcome.