Central poststroke pain: A population-based study Henriette Klit a , Nanna Brix Finnerup a,⇑ , Grethe Andersen b , Troels Staehelin Jensen a,b a Danish Pain Research Center, Aarhus University Hospital, Norrebrogade 44, Building 1A, DK-8000 Aarhus C, Denmark b Department of Neurology, Aarhus University Hospital, Norrebrogade 44, Building 10, DK-8000 Aarhus C, Denmark Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article. article info Article history: Received 27 September 2010 Received in revised form 17 December 2010 Accepted 17 December 2010 Keywords: Neuropathic pain Central pain Stroke Allodynia Hyperalgesia Classification abstract Central poststroke pain (CPSP) is a specific pain condition arising as a direct consequence of a cerebrovas- cular lesion. There is limited knowledge about the epidemiology and clinical characteristics of this often neglected but important consequence of stroke. In this population-based study, a questionnaire was sent out to all (n = 964) stroke patients identified through the Danish National Indicator Project Stroke Data- base in Aarhus County, Denmark, between March 2004 and February 2005. All surviving patients who ful- filled 4 questionnaire criteria for possible CPSP (n = 51) were selected for further clinical examination, and their pain was classified by using stringent and well-defined criteria and a detailed, standardized clinical examination. The minimum prevalence of definite or probable CPSP in this population is 7.3% and the prevalence of CPSP-like dysesthesia or pain is 8.6%. Pinprick hyperalgesia was present in 57%, cold allodynia in 40%, and brush-evoked dysesthesia in 51% of patients with CPSP. Because of its negative impact on quality of life and rehabilitation, pain is an important symptom to assess in stroke survivors. Ó 2010 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved. 1. Introduction Pain after stroke includes a heterogeneous group of conditions including hemiplegic shoulder pain, pain due to spasticity, head- ache, joint pain, and a specific disorder termed central poststroke pain (CPSP) [13]. Although poststroke pains are common, they are an often neglected consequence of cerebral stroke [13], with a negative impact on the quality of life in this group of patients, who already have other major handicaps, such as motor weakness, ataxia, and aphasia [8,26]. For other medical complications after stroke, see Kumar et al. [17]. CPSP is a specific pain condition in which pain is assumed to be the result of a lesion of the normal pain pathways. CPSP was pre- viously defined as ‘‘a neuropathic pain syndrome following stroke characterized by pain and sensory abnormalities in parts of the body that correspond to the cerebrovascular lesion where no other obvious nociceptive, psychogenic, and peripheral neurogenic ori- gin for the pain is present’’ [1,18]. On the basis of a new proposed general definition of neuropathic pain [23], CPSP is now defined as ‘‘pain arising as a direct consequence of a cerebrovascular lesion of the somatosensory system in the central nervous system (CNS)’’ [16]. This new definition raises questions about the epidemiology and clinical characteristics of CPSP as opposed to other types of poststroke pain. Reduced pain and/or temperature sensation, together with allo- dynia (ie, pain elicited by nonnoxious stimuli) or dysesthesia (ie, spontaneous or evoked unpleasant but not painful sensations) in the painful body parts are characteristic features of central pain [1,2,5,6,15,16,18,24]. The sensory loss to thermal and pinprick stimuli is considered to represent damage to the spinothalamic pathways, whereas the hypersensitivity phenomena allodynia and/or dysesthesia may represent a neuronal hyperexcitability [9]. Previous studies of CPSP are mainly based on retrospectively collected data from neurology, pain, or rehabilitation clinics, and not all studies include a clinical examination with well-defined diagnostic criteria of CPSP [9,25]. The lack of stringent criteria for CPSP is reflected in the reported prevalence rates ranging from 1–12% [1,14]. The objectives of the present study were to identify patients with CPSP in a population-based study using a question- naire; to verify the diagnosis by a clinical examination; and to de- scribe the characteristics of CPSP in the identified population. 2. Methods 2.1. Recruitment of stroke patients Stroke patients were identified through the Danish National Indicator Project Stroke Database (NIP, http://www.nip.dk), a data- base in which all hospitalized patients diagnosed with a stroke according to the World Health Organization ICD-10 criteria have been registered since January 2003. The NIP database contains information on risk factors, severity, and treatment of stroke. Pa- tients with intracerebral hemorrhage (I61), cerebral infarction (I63), and unspecified stroke (I64) were included in the study. A questionnaire was sent out in October 2006 to all surviving 0304-3959/$36.00 Ó 2010 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.pain.2010.12.030 ⇑ Corresponding author. Tel.: +45 8949 3455; fax: +45 8949 3269. E-mail address: finnerup@ki.au.dk (N.B. Finnerup). www.elsevier.com/locate/pain PAIN Ò 152 (2011) 818–824