versão impressa ISSN 0004-282X
Arq. Neuro-Psiquiatr. vol.70 no.2 São Paulo fev. 2012
Ecogenicidade da substância negra na doença de Parkinson
Edson Bor-Seng-Shu; Kelson James Almeida; Daniel Ciampi de Andrade; Erich Talamoni Fonoff; Manoel Jacobsen Teixeira; Egberto Reis Barbosa
Hospital das Clínicas, University of São Paulo School of Medicine (FMUSP), São Paulo, Brazil
Idiopathic Parkinson's disease (PD) is a progressive neurodegenerative disorder which affects 1 to 2% of the population over 60 years. The differential diagnosis between PD and atypical Parkinsonian syndromes is usually difficult in the medical practice, mainly in the beginning of clinical manifestation. Modern neuroimaging techniques, such as PET and SPECT, have proved to be useful in the clinical scenario, although expensive and inaccessible1.
Transcranial sonography (TCS) of the brain has recently emerged as a novel diagnostic test for the evaluation of movement disorders1,2. The authors report a patient with PD in whom TCS disclosed hyperechogenicity of the substantia nigra (SN) region; the significance of this finding (SNH) in the clinical practice was discussed.
A 54-year-old female had a 16-year history of PD which followed a characteristic course with gradually worsening symptoms. Hand tremor at rest began initially on the left side and, after 3 years, both sides were affected. Current neurological examination revealed an asymmetric tremor, bradykinesia and muscle rigidity; there were posture and balance dysfunctions, and reduction of automatic movements. Results of brain CT and MRI were normal. TCS of the brain parenchyma disclosed a SN echogenic area greater than 0.20 cm2, bilaterally, fulfilling the criteria for SNH (Figure). Written informed consent was obtained from the patient.
SNH, visualized by TCS, has been considered a biological marker for PD. This ultrasound sign is found in the majority of PD patients (>90%) and has been demonstrated to be associated with functional impairment of the nigrostriatal dopaminergic system1-3.
Animal and human postmortem analyses have attributed increased iron content in the SN as a cause for the hyperechogenicity1,2. It is not known, however, whether increased SN iron levels may cause oxidative stress and secondary neuronal damage or whether SN degenerative process leads to increased iron content in the SN region3.
SNH is less frequently encountered in essential tremor, vascular parkinsonism, multiple system atrophy and progressive supranuclear palsy while this echo feature occurs in most PD patients1,4,5. SNH can be found in a minority of healthy subjects (10%) and they are more likely to develop extrapyramidal signs and symptoms following administration of neuroleptic1,2,5.
Some factors limit the usefulness of TCS, such as its dependence on the operator experience and the lack of temporal acoustic windows (about 10% of patients)1. No correlation was found between the degree of SNH and the severity of dopaminergic innervations impairment4; moreover, SNH seems not to change during the course of PD, so that the progression of PD cannot be monitored by TCS3.
Future longitudinal studies must address if SNH can help to identify PD patients at preclinical stages mainly if considered in conjunction with other nonmotor signs of PD, such as depression, olfactory dysfunction, neuropsychological deficits and idiopathic REM sleep behavior disorder5. If this idea is true, PD could be identified before manifestation of typical signs and symptoms, allowing development of neuroprotective therapies1-5.
1. Berg D, Godau J, Walter U. Transcranial sonography in movement disorders. Lancet Neurol 2008;7:1044-1055. [ Links ]
2. Bor-Seng-Shu E, Fonoff ET, Barbosa ER, Teixeira MJ. Substantia nigra hyperechogenicity in Parkinson's disease. Acta Neurochir (Wien) 2010;152:2085-2087. [ Links ]
3. Berg D, Merz B, Reiners K, Naumann M, Becker G. Five-year follow-up study of hyperechogenicity of the substantia nigra in Parkinson's disease. Mov Disord 2005;20:383-385. [ Links ]
4. Barsottini OG, Felício AC, de Carvalho Aguiar P, et al. Heterozygous exon 3 deletion in the Parkin gene in a patient with clinical and radiological MSA-C phenotype. Clin Neurol Neurosurg 2011;113:404-406. [ Links ]
5. Berg D, Jabs B, Merschdorf U, Beckmann H, Becker G. Echogenicity of substantia nigra determined by transcranial ultrasound correlates with severity of parkinsonian symptoms induced by neuroleptic therapy. Biol Psychiatry 2001;50:463-467. [ Links ]
Divisão de Cirurgia Neurológica, Hospital das Clínicas, USP
Avenida Dr. Eneas de Carvalho Aguiar 255
05403-000 São Paulo SP - Brasil
Conflict of interest:
There is no conflict of interest to declare.
Received 04 September 2011
Received in final form 14 September 2011
Accepted 21 September 2011