Autonomic dysreflexia (AD) is a physiological phenomenon in spinal cord injuries with a neurological level of lesion above T6. Damage at or above T6 interrupts descending modulation of the thoracolumbar sympathetic preganglionic neurons that regulate vasomotor tone (arising from the T5-T12) in the splanchnic vascular bed (Eldahan & Rabchevsky 2018). Aortic and carotid baroreceptors sense hypertension and inform the brain, resulting in vagal stimulation and inhibition of the sympathetic nervous system above the neurological level of lesion (Hickey & Vogel 2002).
Hypertensive episodes in AD occur as a response to noxious visceral or somatic stimulation below the neurological level of the lesion, activating a sympathetic mass reflex leading to widespread vasoconstriction. This is especially common among patients with bladder and bowel problems. AD is defined as an increase in blood pressure of 20-40 mm Hg in adults and 15-20 mm Hg in children (Eldahan & Rabchevsky 2018). This often comes with bradycardia as the parasympathetic innervation is non-affected, though tachycardia seems as frequent. The systolic blood pressure can reach as high as above 300 mm Hg with a risk for brain injury related to the hypertensive crisis, though luckily rare (Kewalrami & Orth 1980).
Other symptoms reported in AD are related to the sympathetic mass reflex and include a pounding headache, pilomotor reflex with goosebump, paresthesia, shivering, flushing, and hyperhidrosis above the neurological level of lesion, nasal obstruction, ocular symptoms including Horner’s syndrome, desire to void, anxiety, malaise, and nausea. There may be a feeling of dullness in the head and blurring of vision. More than 50% of patients experience severe headaches, usually of occipital, bitemporal and bifrontal location, and less frequent a sensation of precordial pressure (Karlsson 1999; Kewalrami & Orth 1980).
Education and prevention are essential in the management of AD (Hickey & Vogel 2002). In addition, It is important to regularly measure blood pressure to find the baseline for comparison and individual monitoring (Zebracki et al. 2013a). Drug treatment must be considered when these measures are inadequate or in the case of an acute hypertensive episode where conservative management is inadequate. A comprehensive consensus-based recommendation involving all these steps is published by Shriner’s Hospitals for Children (McGinnis et al. 2004). A systematic review from 2009 on the management of AD as part of the Spinal Cord Injury Research Evidence project does not specifically include pediatric subjects but gives a comprehensive report of the evidence for different treatments for adults post-SCI (Krassioukov et al. 2009).
Several observational studies and case reports, as well as one case series, examined the prevalence, etiology, and management of AD in the pediatric SCI population. Most of the studies originated from one center, Shriners Hospitals for Children (Hickey & Vogel 2002; Hickey et al. 2004; Hwang et al. 2014a, 2014b; Schottler et al. 2009; Schottler et al. 2012; Vogel et al. 2002b; Zebracki et al. 2013a, 2013b).
As highlighted by Kewalramami and Orth (1980) and Krassioukov (2003), AD can occur, at the earliest, 8 weeks post-injury in children with SCI, but most often presents its first signs 12 to 16 weeks post-injury. Kewalramami and Orth (1980) also found that the onset of AD correlated with the occurrence of a positive bulbocavernosus reflex in their sample of 68 patients. Urologic complications, bladder distension, and bowel impaction were identified as some of the most common causes of AD (Canon et al. 2015; Hickey et al. 2004). Regarding the prevalence of AD in the pediatric SCI population, the studies revealed a rate of around 50% among those with a neurological level of the lesion at T6 and above, which is comparable to that in the adult population (Schottler et al. 2009; Schottler et al. 2012; Vogel et al. 2002b). Complete injuries, traumatic injuries, and older age seemed to be associated with a higher risk of AD (Hickey et al. 2004; Hwang et al. 2014a; Kewalrami & Orth 1980; Schottler et al. 2009; Schottler et al. 2012; Vogel et al. 2002b).
It is worth noting that the lower prevalence of AD in the younger age group may be confounded by factors such as young children’s difficulties in articulating their symptoms as well as differences in the presentation of symptoms between younger and older children. (Hickey et al. 2004). Upon reviewing the medical record of 121 children with SCI who received care at Chicago Shriner’s Hospital for Children, the researchers observed that headache and piloerection were reported less frequently in children with AD who were between ages 0-5 years compared to those between ages 6-13 and 14-21; on the other hand, facial flushing was more commonly reported in the youngest age group compared to that in the two older age groups.
As discussed previously, hyperhidrosis is a common symptom of AD. In one study, McLean et al. (1999) investigated the frequency and clinical implications of environmentally responsive temperature instability in 54 hospitalized pediatric patients with SCI. It was found that 12 (22%) patients experienced a total of 65 episodes of hypothermic events (i.e., oral temperatures less than 35.08 °C or rectal temperatures less than 35.68 °C) and 14 Hyperthermic events (i.e., oral temperatures greater than 38.08 °C or rectal temperatures greater than 38.48 °C). In addition, patients with environmentally responsive temperature instability are more likely to have shorter time post-injury, longer lengths of stay, and be ventilator-dependent than those who did not have environmentally responsive temperature instability (McLean et al. 1999). Through examining a case of a 12-year-old girl with hyperhidrosis from an SCI, Adams et al. (2002) suggested that gabapentin may be an effective therapy for SCI-related hyperhidrosis. However, larger-scale studies are needed to confirm this finding.
Schottler et al. (2009) examined knowledge of AD from the perspectives of youth with SCI and their caregivers, as part of a multicenter study including 215 participants. Participants answered questions concerning the definition, signs and symptoms, and treatment of AD. Not surprisingly, the study found that patients with greater knowledge of AD were more likely to have traumatic etiology, have T6 or higher injuries and shorter duration of injury, and be in older age groups.
The occurrence of AD has not only been linked to various medical complications but also decreased the likelihood of employment in adults with pediatric-onset SCI (Hwang et al. 2014a, 2014b). Therefore, the prevention and management of AD in this population is crucial. Zebracki (2013b) has suggested that one way of preventing and/or identifying early signs of AD in the pediatric SCI population is through the regular assessment and management of baseline blood pressure and heart rate.
The recommendations concerning the management of AD are mainly consensus-based (McGinnis et al. 2004) and/or drawn from anecdotal evidence from case reports (Bjelakovic et al. 2014; Lockwood et al. 2016; Tronnes & Berg 2012), with the exception of a study by Vaidanathan et al. (1998). Vaidyanathan et al. (1998) examined the effectiveness of Terazosin, an alpha-1 blocking agent, in managing symptoms of AD in 24 patients with SCI who had recurrent episodes of AD. Three of the patients were children with SCI who were ventilator-dependent, and 11 were adults with pediatric-onset SCI. The drug was individually titrated with a starting dose of 0.5 mg at bedtime for children and was thereafter titrated with 1.0/0.5 mg every 3-4 days until side effects or problems were resolved. One patient discontinued the medication due to dizziness. For the others, the side effects were self-limiting and noticed only during the first week of treatment and included feelings of tiredness and drowsiness. Following the terazosin therapy, the dysreflexic symptoms subsided completely for all patients. However, the authors note that Terazosin is not the first line of treatment, and should only be considered for selected patients with recurrent episodes of dysreflexia, in whom, it is not possible to identify the predisposing cause, or in whom it is not feasible to abolish the precipitating factor for the AD.