The natural progression of wound botulism varies from mild and insidious to severe and rapidly progressive. Seven strains of C. botulinum exist (A-G), but only A and B strains have been found to be associated with wound botulism secondary to injection drug use [11]. Type A is believed to be the most potent strain and causes the most prolonged disease course [4]. They are all gram positive, anaerobic rods with subterminal spores that thrive in the anaerobic conditions created by subcutaneous abscesses. C. botulinum produces neurotoxin that inhibits acetylcholine release by binding irreversibly to the presynaptic terminal [6, 12]. The resulting clinical syndrome is defined by symmetrical cranial nerve palsies [9, 13]. Mouth dryness, blurry vision, and double vision are reported as earliest neurologic complaints. More severe cases will progress to dysphagia, dysarthria, dysphonia, and peripheral muscle weakness. Furthermore, in its most severe form, a descending flaccid paralysis progresses to involve the respiratory muscles and causes neuromuscular respiratory failure [1, 4]. Notably, patients do not demonstrate any sensory deficits [14]. Recovery is often lengthy and requires generation of new neuromuscular connections [12].
The differential diagnosis should include wound botulism for any patient with a history of BTH use, presenting with generalized weakness and/or bulbar palsies. In addition, it is suggested that ED physicians rapidly request antitoxin, as well as investigating other possible etiologies such as the Miller-Fisher syndrome (MFS) variant of Guillain-Barre syndrome (GBS), myasthenia gravis, stroke syndromes (particularly basilar stroke), Lambert-Eaton Syndrome (LES), tick paralysis, or other generalized neuropathies [9, 15]. Emergency physicians may often have LES or the MFS variant of GBS as their top two differentials, so it is essential for the clinician to differentiate these conditions from botulism. In both botulism and LES, neurotransmitter release is inhibited at the presynaptic motor end plate. However, LES is due to antibodies against presynaptic voltage-gated calcium channels, and these highly specific antibodies can be detected in 85% of LES patients [16]. The MFS variant of GBS is in the differential due to its similar cranial nerve palsies, but it typically causes a noteworthy increase in CSF protein, which can help differentiate it from botulism [2]. Due to similar etiologies, it is imperative that a thorough evaluation be initiated to differentiate these diseases. However, in the case of wound botulism, these ancillary studies, such as serum electrolytes, hemoglobin, hematocrit, computed tomography (CT) of the brain, lumbar puncture, and other diagnostic modalities as indicated, will often be unremarkable [6].
Although neuromuscular transmission studies are often more sensitive, toxin assays are a standard part of diagnostic evaluation in patients suspected of having wound botulism [15]. Serologic testing for wound botulism requires a laboratory with adequate testing capabilities. Serum toxin assays have been reported to have sensitivities as low as 33-44%, whereas neuromuscular transmission studies have been shown in some reports to be diagnostic in up to 100% of cases [2, 15]. Nevertheless, these studies are not suitable for acute diagnosis due to delay in obtaining results. As a consequence, efforts to find a rapid diagnostic tool have shown some promise in creating a sensitive and specific test in PCR-based assays, immunoenzymatic assays, or bead-based suspension array [17].
Treatment of wound botulism with the equine-derived heptavalent (types A-G) or trivalent (types A, B, and E) antitoxin is aimed at interrupting the neurologic progression of the disease and mitigating the duration of ventilatory failure in those who are severely afflicted [6, 18]. The antitoxin neutralizes toxin that has not yet bound to nerve endings, which underscores the importance of early initiation of treatment. Treatment is complete after one dose because one vial generally contains more than enough antibodies to saturate unbound circulating toxin [9]. Additionally, the half-life of the antibodies is 5-8 days. Although antitoxin can be life-saving, clinicians must be aware that 21% of patients receiving antitoxin administration will demonstrate some degree of serum sickness reaction [15]. In severe cases, abscesses must also be drained properly to eradicate the source of bacterial toxins [19].
The morbidity and mortality of wound botulism can be drastically reduced if clinicians are adept at recognizing its clinical predictors. In addition, early recognition of wound botulism and antitoxin administration is critical to minimizing morbidity and mortality [7]. A high clinical suspicion along with a diagnostic and treatment protocol would help accelerate the process [7]. We noticed several diagnostic clues upon presentation which can assist in rapid identification and risk analysis for these individuals. Of note, everyone in this study presented with weakness or fatigue and a history of skin popping. Other common complaints included bulbar palsies (visual changes, difficulty swallowing, vocal changes), shortness of breath, and gait disturbances that were noted in prior reports [4]. Common physical exam findings included skin wounds, extremity weakness, ptosis, extraocular muscle abnormalities, and hypertension [4]. It is important to know that the process of obtaining botulinum antitoxin can be very challenging and time consuming. The local and/or state public health department must first be contacted, and then they contact the CDC. The CDC then arranges delivery of the antitoxin to the requesting hospital using their regional cache of the antitoxins. ED physicians are often unfamiliar with this process, which further prolongs time to administration of the antitoxin.
The generalizability of our findings may be limited. Like many retrospective reviews, the data collected in this study is limited by inconsistent documentation and recording bias. Efforts have been applied to thoroughly review EHR to ensure data accuracy.
