Because infants are unable to describe their symptoms, the onset of
infant botulism can only be detected by careful observation. Usually the first indication
of illness is constipation (defined as decreased frequency in defecation),
although this sign is frequently overlooked by parents and physicians. Generally, parents
first notice that the baby feeds poorly. The breast-feeding mother may notice breast
engorgement because the babys suck is weak. The infant has become lethargic and
listless. Respiratory effort may become shallow and rapid, and the cry is feeble. Drooling
may become more noticeable, which is sometimes attributed to teething rather than to dysphagia.
A "catastrophic" presentation of infant botulism with a paucity of the usual clinical signs has also been recognized. See Nevas et al., Journal of Clinical Microbiology,
2005; Mitchell W, Tseng-Ong L, Pediatrics 2005; 116;436-438; and Hurst and Marsh, The Journal of Pediatrics, 122(6):909-911, 1993.
Because botulinum toxin binds at the neuromuscular junction, the
toxin produces a flaccid motor paralysis that invariably begins in the bulbar musculature.
Somatic musculature is affected next, and patients with rapidly evolving illness may have
generalized weakness, hypotonia and respiratory difficulty when first seen.
On initial presentation, the typical patient has some or all of the
following findings: ptosis (which may not be evident until the infants head is held
erect), weak cry, diminished suck and gag, drooling and/or pooling of saliva, dilated
and/or sluggishly reactive pupils, disconjugate gaze, blunted facial expression, poor head
control, decreased anal sphincter tone, hypotonia and generalized weakness. Deep tendon
reflexes may be either normal or decreased. Sensation remains intact, but this may be
difficult to demonstrate because of the motor paralysis.
In mild cases or in the early stages of illness, the physical signs
of infant botulism may be subtle and easily overlooked. Cranial nerve palsies and the
fatigability of muscular function must be elicited by careful examination. Table 1 below
describes physical examination techniques which have proved helpful in evaluating these
1. PHYSICAL EXAMINATION SIGNS HELPFUL IN THE DIAGNOSIS OF INFANT BOTULISM