Neurology is the medical speciality dealing with the diagnosis and treatment of disorders that involve the central nervous system (brain and spinal cord), peripheral nervous system (nerves) and muscles. Neurological disorders can be diagnosed using various forms of imaging, with magnetic resonance imaging (MRI) providing the most detail of the spinal cord.
When a patient is first admitted, a detailed history will be taken and a neurological examination carried out. Information should be gained on signalment of the animal, onset of the clinical signs and whether they are progressive, if the patient is painful or not and whether it is the brain or spinal cord being affected. This will help to determine how quickly the patient needs treatment. The clinical examination allows the neurologist to localise where they think the problem is occurring. There are seven aspects of the neurological examination; these are: gait/posture, mentation, proprioception, spinal reflex, cranial nerves, palpation and nociception.
Spinal disease is commonly encountered in veterinary practice. There are various spinal conditions that occur in dogs following a traumatic event, such as acute non-compressive nucleus pulposus extrusion (ANNPE), intervertebral disc extrusion (IVDE) and fibrocartilaginous embolism (FCE) (Cardy et al., 2015). Intervertebral disc extrusions are seen frequently; if a patient has an IVDE the disc material could be compressing the spinal cord and it is likely that surgical intervention will be needed.
Patients with spinal disease often present with similar clinical signs, with the most obvious to owners being paraparesis or paraplegia. This can be alongside ataxia, urinary/faecal incontinence and paw positioning deficits. The neurological examination will determine what course of action should be taken.
Chondrodystrophic breeds are predisposed to suffering with IVDE. Breeds such as Dachshunds, Bulldogs, Bassett Hounds, Beagles and Corgis have long bodies and shortened limbs. They are seen to suffer from degenerative discs from early adulthood, making the discs more likely to herniate (Bergknut et al., 2013).
Magnetic resonance imaging has proven to be very valuable in the assessment of pathology within the spine (Weiner and Patel, 2008). MRI uses the body’s natural magnetic properties to produce detailed images. It can be used for all parts of the body, but in veterinary medicine we mostly use it to obtain images of the brain and spinal cord. There are no known biological hazards of using MRI as it uses radiation from the radiofrequency range which is found all around us, causing no harm to tissues. This differs from radiography and computed tomography (CT). It is important to check whether patients needing an MRI have any pacemakers, metal clips or metal valves as these will pull towards the magnetic field, which can be dangerous. Metal joint prostheses or implants, however, can be put through the MRI scanner, but these usually cause artefacts on the image (Berger, 2002). MRI will allow you to identify whether there is any pathology in the spinal cord and gives very detailed images showing how much the spinal cord is being compressed and at what location (Figure 1).
CT scans provide good tissue detail, particularly of bones, generating cross-sectional images over various planes. However, they only show limited detail of the spinal cord, making an MRI scan more useful (Table 1; Platt and Olby, 2013).
Radiographing a patient can be helpful if there is concern about a spinal fracture; however, it will not give any detail of the condition of the spinal cord. Sometimes a radiograph will be taken if the neurologist would like to place a marker on a specific disc space. This will help them identify where they need to do surgery.
Mild cases of IVDE can be managed with medication and cage rest; however, if clinical signs do not improve or if they reoccur, surgery will be necessary. Surgery is generally successful, especially if the patient is nociception-positive on admit. One study showed that 72.5 percent of patients made a complete recovery following surgery (Besalti et al., 2005).
If a patient needs surgical intervention, the surgeon will decide what type of surgery they will perform based on the location of the IVDE. Most commonly, surgery will be a hemilaminectomy. The aim of the surgery is to remove disc material and relieve pressure from the spinal cord.
Following surgery, there is a chance that there will be post-operative neurological deterioration. This makes the post-operative care very important with these patients. They should be kept calm. For a patient you know is anxious, a sedation plan should be made before the end of anaesthesia. Following surgery, they should be cage rested to prevent any further damage being made to the spinal cord and to allow healing time. Once a patient can start being walked, a harness should be used to support them. To ensure the analgesia being given is adequate, a pain scoring system should be used. Analgesic requirements will differ between patients and the degree of hindlimb paresis can make interpretation more challenging than in ambulatory dogs.
Often patients are non-ambulatory post-surgery. In these cases, physiotherapy techniques should be used. Massage and passive range of motion (PROM) are common techniques used. Passive range of motion refers to exercises that move the joints of limbs. It acts to increase blood flow and prevent joint degeneration and muscle contracture. It can also act as analgesia (Burnett and Wardlaw, 2012). Patients generally tolerate massage and PROM very well.
If a neurology patient is unable to urinate post-surgery, their bladder will need to be monitored closely. This can be done using an ultrasound scanner to measure the size and volume of the bladder, and if large, it may need expressing. If the patient you are nursing is fractious or the bladder is difficult to express, a urinary catheter could be considered.
These patients can be hospitalised for several days before being discharged. When discharged, they will often not yet be walking. As long as they are comfortable, are able to urinate and have good movement in limbs affected, owners are able to care for them at home.
MRI is the most accurate and beneficial form of diagnostic imaging to identify a spinal lesion, whether this be a disc extrusion, ANNPE, tumour or FCE. Timing is very important with neurology patients; if the patient is nociception-positive on arrival at the hospital, they have a much better chance of a full recovery. Seeing these patients as soon as possible after a trauma or clinical signs occur is key.