Introduction

Neurotrauma involving the brain and spine has been referred to as the “silent epidemic” in our modern times.¹⁻³ Spinal cord injury (SCI) remains a major public health issue, affecting 900,000 individuals globally.⁴ It is a leading cause of death and permanent disability, with profound impact at both the individual and societal levels. For many years, a bimodal age distribution has characterized the collective epidemiology of this condition, affecting the young (age 15-29 years) and the elderly (≥60 years).⁵ At the turn of the century, however, advances in medical therapeutics and research have resulted in a demographic shift wherein individuals over 65 years of age represent the fastest-growing segment of the population. Although major strides in the realm of public health in high-income countries have been successful in curbing the incidence of SCI due to motor vehicular collisions (MVC), sporting injuries and work-related trauma, the number of elderly individuals suffering from SCI continues to rise dramatically, specifically due to fall-related traumas. Aarabi et al showed that over a 17-year period, the mean age and proportion of SCI due to falls increased significantly, whereas the number of SCIs resulting from MVCs and sports injuries have decreased.⁶ Awareness of the issues specific to older segments of the SCI population have arguably never been more important. In this work, the current status and challenges in the management of elderly SCI patients are examined. We hope this will stimulate a renewed interest in age specific research and development, particularly considering the broader concept of frailty. Demographics Data from the World Health Organization (WHO) indicate that individuals aged >60 years represent 12% of the entire population worldwide.⁷ In the US, individuals within this age group represent the fastest-growing demographic segment.⁸ Medical breakthroughs crucial in reducing fatal diseases, along with improved care of the elderly, have resulted in this major demographic shift. By 2050, it is projected that the proportion of elderly in the global population will increase to 22%, with an absolute number expected to reach up to 2.1 billion.⁷ This upsurge is occurring at an exceptionally fast rate and is expected to continue in the coming decades. While it was previously believed that such unprecedented changes were limited primarily to developed countries, contemporary research suggests that this shift is also occurring in low- and middle-income countries. The UN General Assembly, as part of its declaration of the UN Decade of Healthy Aging (2021-2030), estimates that approximately two-thirds of the world’s population over 60 years will be living in low- and middle-income countries by the end of the decade.⁷ This remarkable demographic change worldwide has resulted in a parallel increase in the incidence of trauma involving the elderly population. Data from the National Trauma Data Bank (NTDB) for 2014 show that more than a third (39%) of all trauma patients were individuals aged >55 years old and death among this group constituted 54% of all reported mortality.⁹ Globally, the temporal trend in the incidence of SCI shows an increasing rate with advancing age. By the year 2032, patients over 70 years will account for the majority of patients sustaining traumatic SCIs.¹⁰ This rapid rise of SCI in the elderly population is further highlighted in a US study that shows an increasing mean age of SCI patients from 40 years in 1993 to 50 years in 2012, most of which were sustained from fall-related injuries.¹¹

Mortality in Geriatric SCI

Varying rates of SCI-related mortality in the elderly have been reported. The rates range from 12-40% and are consistently higher than the rates reported for younger patients.¹² Despite survivorship after traumatic SCI improving steadily since 1970, the mortality rates remain significantly elevated in both the acute and chronic phase of the disease for the elderly.¹³ While urinary tract complications and renal failure were classically thought to be the leading causes of death, more recent investigations suggest that respiratory dysfunction, including pneumonia, is the most common cause of mortality among SCI patients. In older patients, the consequences of prolonged intubation and mechanical ventilation may be substantial. Furlan et al reported an overall rate of mortality as high as 38.6% and that this risk is sustained at 6 weeks, 6 months, and 1 year after injury.¹⁴ The generally uniform finding of increased mortality is consistent with the concept of “biological aging” that leads to altered physiologic reserve and decreased capacity to cope with the systemic stressors of SCI. In general, mortality risk increases as the degree of neurologic impairment rises. However, age at the time of injury has proven to be an equally important determinant of outcome.¹⁵ Various studies have attempted to model the risk predictors for mortality in SCI and these studies note a distinct age-related pattern with higher deaths among older patients.¹²

Morbidity and Complications after SCI

Despite increasing mortality, the rates of surgical treatment for traumatic SCI continue to rise.¹⁶ Elderly patients have more medical problems and are more likely to be on multiple medication regimens. These factors may delay timely surgical intervention. In patients undergoing surgery for decompression and/or stabilization, Ahn et al noted a higher incidence of postoperative complications (eg, UTI, pneumonia, pressure ulcers, DVT) in patients over the age of 70.¹⁷ A recent report that stratified patients into different age groups similarly reported higher rates of complications in patients from 65-69 years old.¹⁶ Interestingly, however, in comparison to younger patients, geriatric patients had similar length of ICU stay with no significant age related differences in rates of neurological improvement. This is a critical point. Due to medical comorbidities, nonoperative treatment has, historically, been more commonly prescribed in elderly patients. This has led to delays in appropriate treatment. Data from a registry study of 1,250 SCI patients stratified into two age groups suggested that older patients were less likely to undergo timely surgical intervention; they experienced more delays in management from time of injury to arrival (triage time) as well as to time from admission to surgery (management time). Both were more than twice as long as the times reported for younger patients.¹⁷ Postoperative delirium is a particular problem in the elderly. In the general spine surgery population, the reported rates range from 0.49 to 21%. In elderly SCI patients, the incidence is 7-9%.¹⁵⁻¹⁶ The consequences of delirium in the elderly population can be significant and may translate to longer hospital length of stay, need for extended care, cognitive dysfunction, postoperative functional decline, dementia and increased mortality. Leslie et al found that delirium in hospitalized non-ICU patients had a 62% increased risk of mortality with an average loss of 13% in life years.²⁰ A clear association between postoperative delirium and old age is noted in a study by Cheung et al and further confirmed by a recent systematic review.²¹⁻²²

Long Term Survivorship and Functional Outcomes

A discussion on the relationship between aging and survivorship after SCI brings into focus two interrelated concepts: i) the increasing age at the time of injury and ii) increasing life expectancy after SCI. The first relationship is generally correlated with the aging population. The maturation of the “baby boomer” generation (birth dates between 1946 and 1964) has led to a geometric increase in the elderly population, especially in Western industrialized countries. At the same time, the life expectancy after SCI has generally improved over the last decade, primarily as a result of improved intensive care and advanced medical and rehabilitation practices. Taken together, these two factors have resulted in an increasing number of patients living with SCI at an advanced age and still suffering with the chronic consequences of the injury. Historically, SCI was considered a fatal disease with poor prospects for survival and recovery. Longitudinal studies of survival rates and life expectancy after SCI, however, have shown remarkable improvement since 1970 corresponding to progress made in SCI therapeutics. Strauss et al reviewed over 30,000 cases of SCI from 1973 to 2004 and identified a 40% decline in mortality, particularly during the first two years after injury.²³ The life expectancy of an SCI patient, however, remains lower compared to the general population.²⁴ A study by DeVivo et al indicated that survival is also adversely affected by age, with only 22.6% surviving among patients >50 years old compared to 86.7% reported in the general population.²⁵ A more recent study by Arul et al reports a similar drop in survival among older patients, albeit with a slightly better estimate of 37.5%.¹⁶ As previously noted, long-term functional outcomes differ between young and old SCI patients. Physiology clearly plays a role. Basic studies into the dynamics of spinal cord repair have shown that age plays a key role in modulating microglial activation, oxidative stress, and regulating the inflammatory cascade during secondary injury.²⁶ Clinical studies of the natural history of patients with SCI, however, have not suggested clear advantages for younger patients in terms of potential for clinical recovery. In fact, in a secondary analysis of the NASCIS 3 trial results by Furlan et al, motor recovery seemed to be better among older patients, but this association was not maintained after adjustment for other confounding variables.¹⁴ Interestingly, sensory recovery was consistently greater in elderly individuals with SCI compared to the younger cohort. A more recent 10-year US database review supports similar in-hospital recovery rates between older and younger patients at time of discharge.²⁶ Likewise, in a cohort of uniformly elderly patients aged >65 years, severity of injury at admission, and not age, was the strongest predictor of functional outcome.²⁷

The Central Issue

As a result of reduced physiologic reserve, multiple comorbidities, and polypharmacy, geriatric patients are more susceptible to falls resulting in SCI with or without concomitant traumatic brain injury (TBI). Anatomically, they are more at risk of significant spinal injury and fractures due to poor bone mineralization, age-related degenerative changes, concurrent osteoporosis and increased spinal rigidity. Age at the time of injury is also related to the type of neurologic injury sustained. Central cord injury is a form of incomplete spinal cord injury secondary to hyperextension in the setting of a narrowed spinal canal and/or pre-existing spondylosis. Typical patients are elderly individuals with no overt signs of spinal instability and may present with a spectrum of symptoms ranging from mild numbness to tetraplegia. In retrospective cohort studies of geriatric patients, central cord syndrome (CCS) was noted to be the most common form of SCI in the elderly.²⁸ Historically, central cord syndrome is treated nonoperatively due to fear of causing further injury in a condition that has a favorable natural history. Recent evidence, however, suggests that early decompression is likely to produce a higher chance of meaningful neurological recovery than delayed surgery.²⁹