International Orthopaedics (2019) 43:957–961 https://doi.org/10.1007/s00264-018-4208-0 REVIEW ARTICLE Cauda equina syndrome—the questions Andrew Quaile1 Received: 27 September 2018 /Accepted: 17 October 2018 /Published online: 29 October 2018 # SICOT aisbl 2018 Abstract Cauda equina syndrome is a devastating condition often following an innocent pathology in the form of a disc prolapse. The effect on sufferers, however, can be lifelong. It is necessary to make a diagnosis as expeditiously as possible via adequate history, clinical examination and appropriate imaging to offer treatment, in the form of decompressive surgery within 48 hours. It is extremely important to communicate adequately with the patient and their family recording all the relevant details including those of expected outcome. National guidelines are likely to be of value to clinicians and patients. Keywords Cauda equina syndrome . MRI scanning . Disc prolapse . Medico-legal . Saddle anaesthesia . Bladder function What is the cauda equina? developed to a stage where there is now complete urinary retention and overflow incontinence. The other features of In 1595, the French anatomist Andre du Laurens first de- cauda equina syndrome are also present although saddle an- scribed the structure of a rope-like tail of fibres at the distal aesthesia is likely to be more dense. Two further categories end of the spinal cord. This bundle of numerous axons was have been proposed, namely CESS, cauda equina suspected named the cauda equina, from the Latin translation meaning and CESC, cauda equina complete [1, 2]. These can be helpful ‘horse’stail’, and it contains nerves which innervate both sen- in terms of entering a treatment pathway and in suspected sory and motor targets within lumbar, sacral and coccygeal cases in the urgency of investigation. Cauda equina syndrome spinal cord levels. These include the legs, perineum, anus is therefore a condition affecting the legs either unilaterally or and bladder. bilaterally with symptoms of back pain but importantly symp- toms of recent onset of bladder function disturbance. Disturbance of bowel function may also be noticed. What is cauda equina syndrome? Cauda equina syndrome is a constellation of symptoms that What are the causes? arise due to impairment of the function of the cauda equina. This is a rare condition most commonly associated with a The most common cause is a massive lumbar disc herniation. massive lumbar disc prolapse. Cauda equina syndrome is di- One to 3% of lumbar disc herniations result in cauda equina vided into CES-I, Cauda Equina Incomplete or CES-R, Cauda syndrome, and its prevalence is one case per 33,000 to one Equina Retention. These two varieties are divided by the ef- case per 100,000 [1, 3]. It results in between 2 and 6% of disc fect on the bladder, CES-I having urinary problems with re- operations or 4 and 7% [2–4]. That said not every massive disc duced bladder sensation and difficulty voiding, sometimes prolapse leads to cauda equina syndrome as pointed out by relying on external pressure. The other features of cauda Cribb et al. in 2007. They noted 15 patients with massive disc equina syndrome such as sciatica, lower limb weakness and prolapses treated non-operatively; 14 showed dramatic reso- saddle anaesthesia are usually present. Whereas CES-R has lution after 24 months, and no patient developed cauda equina syndrome [5]. Cauda equina syndrome can occur after surgery * Andrew Quaile and was responsible for 15% of cases in one study [6]. That [email protected] amounts to an incidence of between 0 and 6.6% depending upon the centre. The associated problems noted were the use 1 Hampshire Clinic, Basing Road, Basingtoke RG24 7AL, UK of Kerrison’s rongeurs as opposed to high-speed drills and the 958 International Orthopaedics (SICOT) (2019) 43:957–961 potential of venous congestion triggered by post-operative What can be comorbidities? oedema. It is therefore very important to monitor the neuro- logical status of post spinal surgery patients very closely, and Venkatesan et al. in 2012 asked if obesity was linked to cauda this monitoring should be recorded. Investigations immediate- equina syndrome. They noted an increase in BMI was indeed ly after open surgery are notoriously difficult to interpret, and linked, postulating a link between the size of disc herniation advice is likely to be necessary from the local imaging depart- and BMI with reduced canal size, electrochemical behaviour ment. Any pathology compressing the cauda equina can cause changes, and inflammatory mediators [9]. This is confirmed the syndrome. Rarer causes would therefore be related to trau- by Cushnie et al. in 2018 who noted that there is an association ma and spinal fractures, tumour or infection resulting in ab- between obesity and cauda equina syndrome due to the poten- scess formation. tial narrowing of the spinal canal due to spinal epidural lipomatosis [10]. What are the symptoms? What history is required? Patients present with a number/constellation of symptoms A complete history of symptoms is very important. This must which include low back pain, unilateral or bilateral sciatica, include a history of the onset of symptoms with particular reduced sensation in the saddle area, reduction of sexual func- emphasis upon any history of saddle anaesthesia and bladder tion, faecal incontinence, bladder dysfunction and lower limb or bowel problems. It should be borne in mind that pain can weakness [1]. The onset of such symptoms can be slow and inhibit bladder or bowel function but there should be a high the actual onset difficult to pin down. Sciatica is a common index of suspicion of serious pathology if these symptoms are complaint but in concert with reduced saddle area sensation, present. It is important, if possible, to determine when symp- and interference with bladder function becomes more signifi- toms of bladder involvement occurred. It is by this that the cant. The onset of perineal problems with bladder function onset of cauda equina syndrome is likely to be measured problems is commonly regarded as being the onset of cauda which is important in regard to both treatment and legal equina syndrome and the time the clock starts ticking. Clinical assessment. suspicion needs to be acted upon urgently. What examination is necessary? Red flags? The examination itself must be thorough and includes examination of the saddle area for loss of sensation and These are symptoms used by primary health practitioners to includes a rectal examination to note the presence or ab- determine whether there is serious pathology which requires sence of anal tone. Gooding et al. noted that rectal exam- onward referral for investigation and treatment. In regard to ination did not discriminate the outcome of MRI scan- cauda equina syndrome, these rely on the presence of bilateral ning. This examination cannot therefore be used to deter- radicular symptoms, with or without bladder problems. These minewhethertorationanMRIscan[11]. Bell et al. noted are very non-specific, and care needs to be taken in evaluation that if it was not possible to exclude the diagnosis of as bilateral leg pain not descending below the knee may sim- cauda equina on clinical grounds, an urgent MRI scan is ply be referred pain rather than true sciatica. Furthermore, recommended [12]. A paper by Balasubramanian et al. cauda equina syndrome can occur with unilateral sciatica. If concluded that saddle anaesthesia had the highest predic- there is no bladder involvement or loss of perineal sensation, tive value in diagnosing MRI scan–proven cauda equina then the patient could be regarded as ‘being at risk’ of cauda compression [13]. equina syndrome although currently not suffering from it. Problems with micturition could be due to pain inhibition rather than to cauda equina syndrome. Examination would What investigations? not show accompanying sensory loss [7]. A paper by Verhagen et al. commented upon red flags and the variance The investigation of choice is an MRI scan. This will be amongst countries in their description for various spinal con- able to determine presence or absence of cauda equina ditions. There was broad agreement in saddle anaesthesia and compression (Fig. 1) from causes such as disc material, sudden onset of bladder dysfunction in nine guidelines; in all, tumour,haematoma,orabscess.Therearethosepatients there were nine red flags in relation to cauda equina although that are so claustrophic that have retained metal fragments only the French guidelines mentioned sciatica [8]. or pacemakers that other methods of either performing an International Orthopaedics (SICOT) (2019) 43:957–961 959 Fig. 1 Axial view showing caudal equina compression Fig. 2 Sagittal view showing very large central disc prolapse MRI scan or using other imaging, such as CT, is neces- this would lead to devitalised tissue and permanent loss sary. A bladder scan is also of value in determining blad- of function in the territory the affected nerve supplies. The der volume in suspected retention. There are those pa- problem with the literature is the classic comparing apples tients with clinical cauda equina syndrome that are ‘scan and oranges as there are not enough patient details for negative’. Hoeritzauer et al. noted 61% in their study with those treated at various time frames and with all the data other studies showing 43 and 48%. It was proposed that on the stage of their individual cauda equina syndrome. there were functional issues. The point is made that im- Patients are therefore treated on a case by case basis. The aging was still required for all patients with possible timing of an MRI scan is discussed in several papers. It cauda equina syndrome to exclude those in which decom- has been proposed that such an investigation should be pression was possible [14]. within one hour in a facility that has such imaging avail- able [2].