torn from the shell rather than let go. Detached pedicellariae may remain active for several hours. The
Toxopneustes sea urchin also has solid spines, but these are nonvenomous.
The venom of sea urchins contains various toxic fractions, including steroid glycosides, hemolysins,
proteases, serotonin, and cholinergic substances. The Pacific Tripneustes urchin carries a neurotoxin with a
predilection for facial and cranial nerves.
Most victims are envenomed when they step on, handle, or brush up against a sea urchin. Because the
creatures tend to be nocturnal, divers are most commonly injured in dark waters during night diving activities,
particularly in small caves or in shallow turbulent waters. Young inquisitive children who explore tidepools
frequently handle urchins incorrectly and may be injured. If a diver moves his hand slowly toward a spiny
(venomous) sea urchin, the spines may align to offer the greatest defense.
Venomous spines inflict immediate and intensely painful stings. The pain is initially characterized by
burning, which rapidly evolves into severe local muscle aching with visible erythema and swelling of the skin
surrounding the puncture site or sites. Frequently a spine breaks off and lodges in the victim. Some sea urchin
spines (such as those of Diadema setosum or Strongylocentrotus purpuratus) contain purplish dye, which may
give a false impression of spines left in the skin. Soft tissue density x-ray techniques or magnetic resonance
imaging may reveal a radiopaque foreign body. If a spine enters a joint, it may rapidly induce severe
synovitis. If multiple spines have penetrated the skin, particularly if they are deeply embedded, systemic
symptoms may rapidly develop, including nausea, vomiting, paresthesias, numbness and muscular paralysis,
abdominal pain, syncope, hypotension, and respiratory distress. The presence of a frank neuropathy may
indicate that the spine has lodged in contact with a peripheral nerve. The pain from multiple stings may be
sufficient to cause delirium. Secondary infections and indolent ulceration are common. A delayed
hypersensitivity-type reaction ("flare-up") at the site of the puncture(s) has been described, in which the
victim demonstrates erythema and pruritus in a delayed fashion (7 to 10 days) post primary resolution from
the initial envenomation. The sensitizing antigen in such cases has yet to be identified.
Two separate unusual cases were reported in 1993 to me by neurologists. In each case the victim sustained
multiple punctures from one or several black sea urchins in Hawaiian waters. The immediate clinical reaction
was typical, but it was followed in 6 to 10 days by severe bulbar polyneuritis with respiratory insufficiency. In
one case the victim was hyporeflexic and appeared to suffer a Guillain-Barrč variation with elevated protein
levels in cerebrospinal fluid; in the other the victim manifested meningoencephalitis documented by magnetic
resonance imaging. The relationship to the urchin stings suggests an autoimmune phenomenon.
A spine that enters a finger in proximity to the nail apparatus may cause a subungual or periungual
granulomatous nodular lesion. Excision may cause permanent nail plate dystrophy.
The stings of pedicellariae are often of greater magnitude, causing immediate intense radiating pain, local
edema and hemorrhage, malaise, weakness, paresthesias, hypesthesia, arthralgias, aphonia, dizziness,
syncope, generalized muscular paralysis, respiratory distress, hypotension, and rarely, death. In some cases
the pain may disappear within the first hour, while the localized muscular weakness or paralysis persists for
up to 6 hours.
The envenomed body part should immediately be immersed in nonscalding hot water (upper limit 113
o
F or 45
o
C) to tolerance for 30 to 90 minutes in an attempt to relieve pain. Any pedicellariae still attached to
the skin must be removed or envenomation will continue. This may be accomplished by applying shaving
foam and gently scraping with a razor. Embedded spines should be removed with care because they easily
fracture. Black or purplish discoloration surrounding the wound after spine removal is often merely spine dye
and therefore may be of no consequence. Although some thin venomous spines may be absorbed within 24
hours to 3 weeks, it is best to remove those that are easily reached. All thick calcium carbonate spines should
be removed because of the risk of infection, foreign body encaseation granuloma, or dermoid inclusion cyst.
External percussion to achieve fragmentation may prove disastrous if a chronic inflammatory process is
initiated in sensitive tissue of the hand or foot. If the spines have acutely entered joints or are closely aligned
to neurovascular structures, the surgeon should take advantage of an operating microscope in an appropriate
setting to remove all spine fragments. The extraction should be performed as soon as possible after the injury.
If the spine has entered an interphalangeal joint, the finger should be splinted until the spine is removed to
limit fragmentation and further penetration. This also may control the fusiform finger swelling commonly
noted after a puncture in the vicinity of the middle or proximal interphalangeal joint. It is inappropriate to
