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REVIEW

Degenerative neurological and neuromuscular disease in young rottweilers A number of idiopathic degenerative diseases affecting the central nervous system, peripheral nerves and muscles of immature and young adult rottweilers are reported. Tetraparesis or ataxia causing abnormalities in gait and posture are clinical findings common to

of the central nervous system (CNS). In addition to the degenerative disorders outlined in this report, a wide range of conditions affecting the spine and spinal cord are possible and have been reported in young rottweilers (Table 2).

these conditions. The current knowledge about these syndromes is presented in this review, with an emphasis on the clinical characteristics. Knowledge of these syndromes and a methodical approach to neurological diagnosis can help the veterinarian to identify the underlying disease and establish a prognosis when presented with a tetraparetic or ataxic young rottweiler. D. R. DAVIES AND P. J. IRWIN Journal of Small Animal Practice (2003) 44, 388–394

INTRODUCTION Early-onset neurological and muscular diseases in the dog are often a result of inherited defects and are frequently degenerative in nature. The signalment of the patient and the exclusion of other known disorders are of critical importance in the correct identification of these disorders (Coates and Kline 1995), as definitive antemortem testing is usually not possible. The rottweiler breed has had several such diseases described in the literature since the early 1980s (Table 1) and, therefore, provides the veterinary practitioner with particular difficulty when neurological signs occur at a young age. The aims of this paper are to review the current knowledge about degenerative neurological and neuromuscular diseases of the young (less than four years old) rottweiler, and to present the veterinarian with guidelines for clinical diagnosis based on neuroanatomical principles.

UPPER MOTOR NEURON DISEASES

School of Veterinary Clinical Science, Division of Veterinary and Biomedical Sciences, Murdoch University, South St, Murdoch, Western Australia 6150, Australia

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Upper motor neuron (UMN) diseases produce clinical signs of paresis (loss of voluntary motor activity), ataxia (lack of coordination), hyperreflexia and hypertonia of the limbs distal to the affected area

Neuroaxonal dystrophy and leucoencephalomalacia The two principal degenerative UMN diseases that affect young rottweilers are neuroaxonal dystrophy (NAD) and leucoencephalomalacia, or leucoencephalomyelopathy (LEM). These diseases were first reported in the early 1980s (Cork and others 1983, Gamble and Chrisman 1984) and were reviewed in detail by Chrisman (1992). Ataxia is the prominent clinical abnormality in both diseases, and neurological examination is consistent with a cervical myelopathy. Results of ancillary testing in both diseases are unremarkable. Both diseases are thought to be inherited by an autosomal recessive mechanism (Cork and others 1983, Wouda and van Nes 1986). NAD has been reported in the USA (Cork and others 1983, Chrisman and others 1984, Evans and others 1988), Spain (Boersma and others 1995) and Australia (Bennett and Clarke 1997). Clinical signs of NAD begin before the age of 12 months, but are initially subtle and may be dismissed as clumsiness in a largebreed puppy (Chrisman 1992). Hypermetria of the forelimbs is often marked. Some authors report decreased conscious proprioceptive responses (Cork and others 1983, Evans and others 1988, Boersma and others 1995). Cerebellovestibular signs, such as head tremor and nystagmus, develop later in the course of the disease, but strength is maintained and survival for some years is possible. Histologically, characteristic axonal spheroids are most prominent in the spinal cord dorsal horn grey matter, the nucleus of the dorsal spinocerebellar tract, the vestibular nucleus, the nucleus gracilis, the lateral cuneate and cuneate nuclei (Cork and others 1983, Chrisman 1992), and

JOURNAL OF SMALL ANIMAL PRACTICE

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Table 1. Degenerative neurological and neuromuscular diseases seen in young rottweilers Syndrome

Age of onset

Neurological signs

Other features

First reported

Ataxia, hypermetria of forelimbs, hyperreflexia, crossed extensor reflexes. Head ataxia/tremor, nystagmus, menace deficit later. Nociception normal. Some authors report decreased conscious proprioception Ataxia, hypermetria of forelimbs, hyperreflexia, crossed extensor reflexes, decreased conscious proprioception. Tetraparesis develops within weeks to months. Spinal signs only

Skeletal muscles normal. Ancillary tests normal. Slowly progressive with maintenance of strength for years in some cases

Cork and others (1983)

Skeletal muscles normal. Ancillary tests normal. Most patients euthanased within 6 to 12 months

Gamble and Chrisman (1984)

Tetraparesis, hyporeflexia, decreased postural reactions, head tremor, limb tremors, reduced gag reflex, nociception normal. Muscle atrophy and extensor rigidity develop Paraparesis progressing to tetraparesis, hyporeflexia, hypotonia, muscle atrophy, plantigrade stance. Normal cranial nerves and nociception. Slowly progressive ± relapsing

Regurgitation may be present from an early age. Mild increase in serum CK. EMG: denervation potentials, decreased motor NCV, depressed DEMP. All cases euthanased by 11 weeks of age Positive sharp waves and fibrillation potentials on EMG, especially distal muscles; decreased NCV. Apparent response to corticosteroids. Survival data unavailable

Shell and others (1987a,b)

Tetraparesis worse in hindimbs, decreased reflexes and postural reactions. Moderate distal appendicular muscle atrophy in 1 out of 5 cases

Laryngeal paralysis. Positive sharp waves and fibrillation potentials in laryngeal and appendicular muscles on EMG. Low to normal NCV, low DEMP, RNS normal. 4 out of 5 with cataracts. 4 out of 5 cases euthanased within 10 weeks

Mahony and others (1998)

6 to 16 weeks

Ataxia, dysmetria, paraparesis progressing to tetraparesis. Spinal reflexes variable, conscious proprioception decreased. Head tremor, positional strabismus, nystagmus

Laryngeal paralysis (with abnormal EMG) and dysphagia often present. Other ancillary tests normal. Often rapidly progressive, although survival of 9 months reported. 2 Australian cases with cataracts

Kortz and others (1995), Mandigers and others (1995)