Original ArticlesRelationship between nailfold plexus visibility and clinical, neuropsychological, and brain structural measures in schizophrenia
Introduction
The subpapillary plexus is the vascular network at the base of the finger nailfold into which capillaries drain. It is normally visible at birth, but by adolescence visibility becomes increasingly rare, and after puberty only a few individuals have visible plexus Maricq 1964, Whitson and Jones 1971. The mechanism underlying plexus visibility is unknown but is likely to be related to the thinness or transparency of the skin. Although some studies have reported morphological abnormalities of the capillary endrow loops in the nailbeds of patients with schizophrenia Hauptmann and Myerson 1948, Norris and Chowning 1964, plexus visibility refers specifically to the visibility, not morphology, of the vasculature.
Adult plexus visibility has been repeatedly demonstrated to be associated with schizophrenia (Clementz et al 1992b, Maricq 1963a, Maricq 1969, Norris and Chowning 1964; but for reviews see Iacono 1985, Poole et al 1991). It has been reported that between 17% and 72% of persons with schizophrenia have highly visible plexus Clementz et al 1992b, Hauptmann and Myerson 1948, Maricq 1963a, while only about 6% of the general population have the trait Clementz et al 1992b, Maricq 1977. A high plexus visualization score (PVS; Maricq 1970), a quantitative index reflecting the amount of visible plexus, does not appear to be associated with other psychiatric disorders such as bipolar disorder and major depression, even when such patients are psychotic (Clementz et al 1992b).
A few studies have investigated the genetic transmission of plexus visibility and its association with schizophrenia and schizotypy in relatives. Maricq and Jones (1976)found that 78% of high PVS non–psychiatric teenagers had at least one parent with high PVS. Only 7% of the low PVS teens had parents with high PVS, which is close to the expected base rate of high PVS in a normal population. A family study conducted by Buchanan and Jones (1969) reported a .56 rank-order correlation between plexus scores and schizotypy ratings among first-degree relatives (40 siblings and 66 parents) of high plexus schizophrenia probands. A study by Clementz et al 1992a, Clementz et al 1992b showed that high plexus visibility was not found in greater proportions in the relatives of probands experiencing their first-episode of schizophrenia. However, the relatives of high PVS schizophrenia probands had higher PVS than relatives of low PVS schizophrenia probands.
Increased visibility of the nailfold plexus has also been shown to be more strongly associated with familial than with sporadic schizophrenia. Maricq (1963b) reported that 70% of patients with familial schizophrenia and 19% of patients with sporadic schizophrenia had high PVS. Maricq et al (1968) demonstrated that first-degree relatives of schizophrenia patients with high PVS have almost a three-fold risk for schizophrenia compared to the risk for relatives of patients with low PVS. She and her colleagues found that 10% of the low PVS probands had an affected first-degree relative, whereas 28% of the high PVS probands had an affected relative. Almost identical figures were derived from a large state–hospital sample in which 30% of high PVS schizophrenia probands, compared to 13% of low PVS probands, had a first-degree relative with schizophrenia (Poole 1993).
It is known that the skin and brain both develop from the same ectodermal tissue and thus abnormalities of the skin may provide clues from which inferences about brain development and integrity can be made. Unfortunately, very little is known about the relationship between plexus visibility and neuropsychological or brain structural integrity in schizophrenia. Indeed, it is a large theoretical leap from the nailfold to the brain when one tries to link plexus visibility to neurological and cognitive deficits because of the dearth of research into these matters. There is some evidence that plexus visibility may be associated with a liability for neurological dysfunction. One study by Alson (1965) found that schizophrenia patients with high PVS ratings performed more poorly than those with low PVS ratings on the following cognitive and motor tasks: visual reaction time, writing serial Xs for 90 seconds, Memory for Digits (backward; there were no differences when digits were recalled forward), the Quick Test, Porteus Maze Test, Absurd Sentences, and tests of pattern learning.
Other evidence that plexus visibility might be related to neurological dysfunction comes from 2 recent studies that found that plexus visibility was associated with negative symptoms but not positive or affective symptoms. The first study (Poole et al 1991), using a sample of severely affected chronic schizophrenia patients, found a moderately strong correlation (r = .49) between PVS ratings and negative symptoms including motor, expressive, cognitive, and motivational deficits. However, the effects of neuroleptic medications and long-term hospitalization could not be ruled out as playing a role in the specific relationship of plexus visibility and negative symptoms. These confounds were the focus of the second study (Poole et al 1993), in which a medication-controlled design was employed with a less severely affected schizophrenia sample. PVS ratings were again correlated with motor and expressive deficits (r = .45), specifically flat affect, poverty of speech, and catatonic behavior.
Aside from the finding that plexus visibility is associated with schizophrenia, which has been replicated many times without failure, the significance of this association remains something of a mystery. Most of what we do know is limited in that it is based on research conducted prior to 1970 using outdated and relatively unsophisticated methodology. The current study attempts to shed some light on the nature of nailfold plexus visibility by investigating its relation to neuropsychological functioning, brain morphology, and clinical features in a large epidemiological sample of first episode psychotic patients and chronic schizophrenia patients. Also of great interest is the relationship between plexus visibility and smooth-pursuit eye tracking, a well-researched marker for schizophrenia liability Iacono and Clementz 1993, Levy et al 1993.
Section snippets
Sample
One-hundred and forty-one persons (97 men and 44 women) experiencing their first lifetime episode of psychosis (i.e., all had hallucinations and/or delusions) participated in the study. First episode patients were drawn from a large epidemiological study of the course of psychosis, the Markers and Predictors of Psychosis project (MAP) (see Iacono and Beiser [1989] for details of the study and a description of the recruitment of these participants). To avoid potential biases involved with
Results
Preliminary one-way ANOVAs indicated that there were no age, gender, or medication effects on plexus visibility scores. This is consistent with previous studies of plexus and schizophrenia Clementz et al 1992b, Poole et al 1993.
Discussion
The present study replicated the finding that visibility of the vascular plexus at the nailfold is specifically related to the diagnosis of schizophrenia, this time using an 18-month longitudinal diagnosis. Almost one–fourth of the chronic and first–episode schizophrenia and schizophreniform patients had highly visible plexus. Approximately 7% of the nonpsychiatric controls and psychiatric controls that had a mood disorder with psychotic features had highly visible plexus. Less than 8% with
Acknowledgements
This work was supported by grants from the National Institute of Mental Health (MH 49738 and MH 17069). Portions of this paper were presented at the 1997 International Congress on Schizophrenia Research in Colorado Springs, Colorado.
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