Neurologisch onderzoek bij paarden in de praktijk

A thorough neurologic examination is required when a horse shows signs of neurological disease or when it has to be confirmed that the horse is neurologically normal. The main purpose of the examination is to investigate whether there are neurological deficits. In addition, the identification of the primary cause and localization of the lesion should be attempted. A standardized head-to-tail approach helps to avoid overlooking important lesions. Therefore, the examination always starts with a thorough patient history, observation of the horse with special attention to mental state, behavior, posture and stance, and a clinical examination. Subsequently, the cranial nerves are tested by investigating, amongst others, the menace, light and palpebral responses. The neck, trunk, limbs and tail are examined for asymmetry or hypo-or hypersensitivity. Afterwards, the movements of the horse are inspected. Incoordination of the horse is accentuated during transitions, small circles and zig zag lines. However, the difference with orthopedic problems is not always easy to make. Especially horses in lateral recumbency present an extra challenge as recumbency itself may cause a change in responses. Further examinations are often necessary to confirm neurologic disease or to visualize a lesion. Blood examination (general, serology, virus isolation), liver or muscle biopsies, examination of cerebrospinal fluid and radiographs are feasible to perform in practice. In specialized hospitals, electro-diagnostic tests and advanced medical imaging (CT, M RI, scintigraphy) are available. By combining these techniques with the clinical neurologic examination, a (differential) diagnosis can be made

Accuracy of transcranial magnetic stimulation and a Bayesian latent class model for diagnosis of spinal cord dysfunction in horses

Background: Spinal cord dysfunction/compression and ataxia are common in horses. Presumptive diagnosis is most commonly based on neurological examination and cervical radiography, but the interest into the diagnostic value of transcranial magnetic stimulation (TMS) with recording of magnetic motor evoked potentials has increased. The problem for the evaluation of diagnostic tests for spinal cord dysfunction is the absence of a gold standard in the living animal. Objectives: To compare diagnostic accuracy of TMS, cervical radiography, and neurological examination. Animals: One hundred seventy-four horses admitted at the clinic for neurological examination. Methods: Retrospective comparison of neurological examination, cervical radiography, and different TMS criteria, using Bayesian latent class modeling to account for the absence of a gold standard. Results: The Bayesian estimate of the prevalence (95% CI) of spinal cord dysfunction was 58.1 (48.3%-68.3%). Sensitivity and specificity of neurological examination were 97.6 (91.4%-99.9%) and 74.7 (61.0%-96.3%), for radiography they were 43.0 (32.3%-54.6%) and 77.3 (67.1%-86.1%), respectively. Transcranial magnetic stimulation reached a sensitivity and specificity of 87.5 (68.2%-99.2%) and 97.4 (90.4%-99.9%). For TMS, the highest accuracy was obtained using the minimum latency time for the pelvic limbs (Youden's index = 0.85). In all evaluated models, cervical radiography performed poorest. Clinical Relevance: Transcranial magnetic stimulation-magnetic motor evoked potential (TMS-MMEP) was the best test to diagnose spinal cord disease, the neurological examination was the second best, but the accuracy of cervical radiography was low. Selecting animals based on neurological examination (highest sensitivity) and confirming disease by TMS-MMEP (highest specificity) would currently be the optimal diagnostic strategy

Magnetic motor evoked potentials of cervical muscles in horses

Background: When surgical treatment of cervical vertebral malformation is considered, precise localization of compression sites is essential, but remains challenging. Magnetic motor evoked potentials (mMEP) from paravertebral muscles are useful in localizing spinal cord lesions, but no information about cervical muscle mMEP in horses is available yet. Therefore, the aim of this study was to determine the possibility, normal values, inter-and intra-observer agreement and factors that have an effect on cervical mMEP in healthy horses. Methods: Transcranial magnetic stimulation was performed on 50 normal horses and 4 (2 left, 2 right) muscle responses were recorded at the middle of each cervical vertebra (C1-C7) and additionally just caudal to C7 to evaluate cervical nerves (Cn) Cn1 to Cn8. Latency time and amplitude of the recorded mMEP were defined by both an experienced and an unexperienced operator. Results: Latency increased gradually from 14.2 +/- 1.38 ms for Cn3 to 17.7 +/- 1.36 ms for Cn8, was significantly influenced by cervical nerve (P < 0.01), gender (P = 0.02) and height (P = 0.03) and had a good intra-observer agreement. The smallest mean amplitude (4.35 +/- 2.37 mV) was found at Cn2, the largest (5.99 +/- 2.53 mV) at Cn3. Amplitude was only significantly influenced by cervical nerve (P < 0.01) and had a low intra-observer agreement. No significant effect of observer on latency (P = 0.88) or amplitude (P = 0.99) measurements was found. Conclusion: mMEP of cervical muscles in normal horses are easy to collect and to evaluate with limited intra-and inter-observer variation concerning amplitude and should be investigated in future studies in ataxic horses to evaluate its clinical value

Determination of magnetic motor evoked potential latency time cutoff values for detection of spinal cord dysfunction in horses

Background: Transcranial magnetic stimulation (TMS) and recording of magnetic motor evoked potentials (MMEP) can detect neurological dysfunction in horses but cutoff values based on confirmed spinal cord dysfunction are lacking. Objectives: To determine latency time cutoff for neurological dysfunction. Animals Five control horses and 17 horses with proprioceptive ataxia. Methods: Case-control study with receiver operating characteristic curve analysis, based on diagnostic imaging, TMS, and histopathological findings. Horses were included if all 3 examinations were performed. Results: Diagnostic imaging and histopathology did not show abnormalities in the control group but confirmed spinal cord compression in 14 of 17 ataxic horses. In the remaining 3 horses, histopathological lesions were mild to severe, but diagnostic imaging did not confirm spinal cord compression. In control horses, latency time values of thoracic and pelvic limbs were significantly lower than in ataxic horses (20 +/- 1 vs 34 +/- 16 milliseconds, P = .05; and 39 +/- 1 vs 78 +/- 26 milliseconds, P = .004). Optimal cutoff values to detect spinal cord dysfunction were 22 milliseconds (sensitivity [95% CI interval], 88% [73%-100%]; specificity, 100% [100%-100%]) in thoracic and 40 milliseconds (sensitivity, 94% [83%-100%]; specificity, 100% [100%-100%]) in pelvic limbs. To detect spinal cord dysfunction caused by compression, the optimal cutoff for thoracic limbs remained 22 milliseconds, while it increased to 43 milliseconds in pelvic limbs (sensitivity, 100% [100%-100%]; specificity, 100% [100%-100%] for thoracic and pelvic limbs). Conclusions and Clinical Importance: Magnetic motor evoked potential analysis using these cutoff values is a promising diagnostic tool for spinal cord dysfunction diagnosis in horses

Diagnostic aid of transcranial magnetic stimulation in horses suspected of neurological gait abnormalities: a retrospective study

Movement disorders are often found in horses. A good clinical, neurological and orthopedic examination often reveals the cause of the abnormal gait. However, in more complex cases, assessing whether the horse has an orthopedic or neurological problem may be challenging. Between 01/10/2013 and 30/06/2015, 138 horses were examined by transcranial magnetic stimulation (TMS) because of gait abnormalities. The technique, which assesses the functionality of the descending motor tracts, was performed as described by Nollet et al. (2004). In 71 horses (51%), TMS was normal. Further examination revealed an orthopedic or conformational gait abnormality in 59 (83%) of these horses. However, in 12 cases (17%) a neurologic gait abnormality was diagnosed. Proprioceptive ataxia was suspected in 6 of them, 5 had a central or vestibular nervous problem and 1 had painful neck lesions. Of the 67 cases (48%) with an abnormal TMS, 30 owners declined further examinations. In the other 37 horses X-rays of the suspected region were taken and in 6 cases a contrast myelogram was performed in addition. Arthrosis of the facet joints of C5 to T11 (6 horses, 50%), cervical vertebral malformation (8 cases, 25%), trauma (6 cases, 19%: 2 fractures, 3 subluxations and 1 hematoma), neoplasia (1 case, 3%) and intervertebral disk disease (1 case, 3%) were found. So, in 32 cases (87%) spinal ataxia was confirmed by medical imaging. In conclusion, transcranial magnetic stimulation is a sensitive and specific aid in examining gait abnormalities in horses