Intracranial aneurysms in autosomal dominant polycystic kidney disease

Genetics Of Intracranial Aneurysms

Despite advances in the treatment of intracranial aneurysms (IA) in recent years, the overall outcome of patients with aneurysmal subarachnoid hemorrhage has shown only modest improvement. Given this poor prognosis, diagnosis of IA before rupture is of paramount importance. Currently, there are no reliable methods other than screening imaging studies of high-risk individuals to diagnose asymptomatic patients. Multiple levels of evidence suggest that environmental factors acting in concert with genetic susceptibilities lead to the formation, growth, and rupture of aneurysms in these patients. Epidemiological studies have already identified aneurysm-specific risk factors such as size and location, as well as patient-specific risk factors, such as age, sex, and presence of medical comorbidities, such as hypertension. In addition, exposure to certain environmental factors such as smoking have been shown to be important in the formation of IA. Furthermore, substantial evidence proves that certain loci contribute genetically to IA pathogenesis. Genome-wide linkage studies using relative pairs or rare families that are affected with the Mendelian forms of IA have already shown genetic heterogeneity of IA, suggesting that multiple genes, alone or in combination, are important in the disease pathophysiology. The linkage results, along with association studies, will ultimately lead to the identification of IA susceptibility genes. Identification of the genes important in IA pathogenesis will not only provide novel insights into the primary determinants of IA, but will also result in new opportunities for early diagnosis in the preclinical setting. Ultimately, novel therapeutic strategies based on biology will be developed, which will target these newly elucidated genetic susceptibilities.

Renal and extrarenal manifestations of autosomal dominant polycystic kidney disease

The objective of the present study was to determine the frequency of the most common clinical features in patients with autosomal dominant polycystic kidney disease in a sample of the Brazilian population. The medical records of 92 patients with autosomal dominant polycystic kidney disease attended during the period from 1985 to 2003 were reviewed. The following data were recorded: age at diagnosis, gender, associated clinical manifestations, occurrence of stroke, age at loss of renal function (beginning of dialysis), and presence of a family history. The involvement of abdominal viscera was investigated by ultrasonography. Intracranial alterations were prospectively investigated by magnetic resonance angiography in 42 asymptomatic patients, and complemented with digital subtraction arteriography when indicated. Mean age at diagnosis was 35.1 +/- 14.9 years, and mean serum creatinine at referral was 2.4 +/- 2.8 mg/dL. The most frequent clinical manifestations during the disease were arterial hypertension (63.3%), lumbar pain (55.4%), an abdominal mass (47.8%), and urinary infection (35.8%). Loss of renal function occurred in 27 patients (mean age: 45.4 +/- 9.5 years). The liver was the second organ most frequently affected (39.1%). Stroke occurred in 7.6% of the patients. Asymptomatic intracranial aneurysm was detected in 3 patients and arachnoid cysts in 3 other patients. In conclusion, the most common clinical features were lumbar pain, arterial hypertension, abdominal mass, and urinary infection, and the most serious complications were chronic renal failure and stroke. Both intracranial aneurysms and arachnoid cysts occurred in asymptomatic patients at a frequency of 7.14%.

Natural history and general management of unruptured intracranial aneurysms

After an aneurysmal subarachnoid hemorrhage, nearly half of the patients die and the half who survive suffer from irreversible cerebral damage. With increasing use of noninvasive neuroimaging techniques (for example, magnetic resonance and computerized tomography angiography), more unruptured cerebral aneurysms are found. To understand the prevalence of unruptured aneurysms in the general population, along with the risks of aneurysm formation, data on growth and rupture rates are crucial. The risk of rupture in aneurysms smaller than 10 mm is still not quite clear without a population-based prospective study. Nevertheless, a 0.5 to 2% annual risk may be a reasonable estimate. Growing aneurysms and those larger than 10 mm carry a higher rate of rupture. The management of an unruptured intracranial aneurysm should be based on a thorough understanding of the natural history of these lesions and careful evaluation of the morbidity and mortality levels associated with each treatment option.

Autosomal dominant polycystic kidney disease (ADPKD, MIM 173900, PKD1 and PKD2 genes, protein products known as polycystin-1 and polycystin-2)

Autosomal dominant polycystic kidney disease (ADPKD) is a common inherited nephropathy affecting over 1:1000 of the worldwide population. It is a systemic condition with frequent hepatic and cardiovascular manifestations in addition to the progressive development of renal cysts that eventually result in loss of renal function in the majority of affected individuals. The diagnosis of ADPKD is typically made using renal imaging despite the identification of mutations in PKD1 and PKD2 that account for virtually all cases. Mutations in PKD1 are associated with more severe clinical disease and earlier onset of renal failure. Most PKD gene mutations are loss of function and a 'two-hit' mechanism has been demonstrated underlying focal cyst formation. The protein products of the PKD genes, the polycystins, form a calcium-permeable ion channel complex that regulates the cell cycle and the function of the renal primary cilium. Abnormal cilial function is now thought to be the primary defect in several types of PKD including autosomal recessive polycystic kidney disease and represents a novel and exciting mechanism underlying a range of human diseases.

A 4-year-old girl with autosomal dominant polycystic kidney disease complicated by a ruptured intracranial aneurysm

In patients with autosomal dominant polycystic kidney disease (ADPKD), intracranial aneurysms (ICAs) are extrarenal manifestations and may result in serious and potentially fatal outcome following rupture. Although ICAs are a well-known complication of ADPKD, nearly all cases of ICA occurring in the context of ADPKD are adults. Here, we report the case of a Japanese girl with ADPKD who developed a subarachnoid haemorrhage (SAH) due to a ruptured ICA at the age of 4 years.

CONCLUSION

This report is intended to raise awareness that the use of noninvasive screening techniques such as three-dimensional CT angiography or magnetic resonance angiography to detect intracranial aneurysms should also be performed in paediatric patients with autosomal dominant polycystic kidney disease.

Regulation of calcium signaling by polycystin-2

Autosomal dominant PKD (ADPKD) is a common lethal genetic disorder characterized by progressive development of fluid-filled cysts in the kidney and other target organs. ADPKD is caused by mutations in the PKD1 and PKD2 genes, encoding the transmembrane proteins polycystin-1 (PC1) and polycystin-2 (PC2), respectively. Although the function and putative interacting ligands of PC1 are largely unknown, recent evidence indicates that PC2 behaves as a TRP-type Ca2+-permeable nonselective cation channel. The PC2 channel is implicated in the transient increase in cytosolic Ca2+in renal epithelial cells and may be linked to the activation of subsequent signaling pathways. Recent studies also indicate that PC1 functionally interacts with PC2 such that the PC1-PC2 channel complex is an obligatory novel signaling pathway implicated in the transduction of environmental signals into cellular events. The present review purposely avoids issues of regulation of PC2 expression and trafficking and focuses instead on the evidence for the TRP-type cation channel function of PC2. How its role as a cation channel may unmask mechanisms that trigger Ca2+transport and regulation is the focus of attention. PC2 channel function may be essential in renal cell function and kidney development. Nonrenal-targeted expression of PC2 and related proteins, including the cardiovascular system, also suggests previously unforeseeable roles in signal transduction.

Altered Arterial Homeostasis and Cerebral Aneurysms: A Review of the Literature and Justification for a Search of Molecular Biomarkers

DESPITE THE CATASTROPHIC consequence of ruptured intracranial aneurysms, very little is understood regarding their pathogenesis, and there are no reliable predictive markers for identifying at-risk individuals. Given that intracranial aneurysms have a strong but complex genetic component and well-characterized modifiable risk factors, it seems likely that the most valuable approach to developing minimally invasive diagnostic and prognostic tools will involve a multifactorial model that includes both genetic and environmental risk factors. Unfortunately, the genetic basis of intracranial aneurysms is poorly described, and reports describing the association of nonrandom deoxyribonucleic acid sequence variation with intracranial aneurysms have been limited to a handful of ad hoc studies that have focused on a variety of markers in small populations. One reason for this lack of coordinated analysis of the genetic basis of intracranial aneurysms is that the molecular pathogenesis and pathobiological characteristics of the disease are poorly described, so candidate marker selection has been problematic. Few studies have addressed the molecular pathological basis of intracranial aneurysms or the possible mechanisms of intracranial aneurysm formation. In this regard, candidate gene selection strategies have relied almost exclusively on limited knowledge of monogenic disorders such as Ehlers-Danlos syndrome and Marfan's syndrome, in which intracranial aneurysm is a feature of a spectrum of syndromic phenotypes. Without exception, these approaches have not affected the clinical identification and/or management of intracranial aneurysms significantly. Therefore, it is imperative that coordinated large-scale efforts in genetics, molecular biology, and genetic epidemiology are implemented to overcome these obstacles and drive developments in the field. In this review, we summarize the current screening modalities for intracranial aneurysms, review the current state of understanding relating to the genetic basis of intracranial aneurysms, and suggest a broader theory of aneurysm pathogenesis to form the foundation of a coordinated molecular search for biological markers that may be associated with aneurysm formation and rupture.

Screening for intracranial aneurysms in autosomal dominant polycystic kidney disease. Review Article

Screening patients with autosomal dominant polycystic kidney disease (ADPKD) for asymptomatic intracranial aneurysms has been proposed as a method of reducing the morbidity and mortality associated with aneurysm rupture. However, recent studies have shown lower spontaneous rupture rates of small aneurysms and higher risks of significant complications with interventions than previously reported. Risk-benefit analysis has not demonstrated any benefit of screening ADPKD patients without a history of subarachnoid haemorrhage (SAH) for intracranial aneurysms, and has suggested that screening might cause harm.

Pkd2 haploinsufficiency alters intracellular calcium regulation in vascular smooth muscle cells

Autosomal-dominant polycystic kidney disease is a multiorgan disease and its vascular manifestations are common and life-threatening. Despite this, little is known about their pathogenesis. Somatic mutations to the normal PKD allele in cystic epithelia and cyst development associated with the unstable Pkd2(WS25) allele suggest a two-hit model of cystogenesis. However, it is unclear if this model can account for the cardiovascular pathology or if haploinsufficiency alone is disease-associated. In the present study, we found a decreased polycystin-2 (PC2, protein encoded by Pkd2 gene) expression in Pkd2( +/-) vessels, roughly half the wild-type level, and an enhanced level of intracranial vascular abnormalities in Pkd2 (+/-) mice when induced to develop hypertension. Consistent with these observations, freshly dissociated Pkd2 (+/-) vascular smooth muscle cells have significantly altered intracellular Ca(2+) homeostasis. The resting [Ca(2+)](i) is 17.1% lower in Pkd2 (+/-) compared with wild-type cells (P=0.0003) and the total sarcoplasmic reticulum Ca(2+) store (emptied by caffeine plus thapsigargin) is decreased (P<0.0001). The store operated Ca(2+) (SOC) channel activity is also decreased in Pkd2 (+/-) cells (P=0.008). These results indicate that inactivation of just one Pkd2 allele is sufficient to significantly alter intracellular Ca(2+) homeostasis, and that PC2 is necessary to maintain normal SOC activity and the SR Ca(2+) store in VSMCs. Based on these findings, and the fact that [Ca(2+)](i) signaling is essential to the regulation of contraction, production and secretion of extracellular matrix, cellular proliferation and apoptosis, we propose that the abnormal intracellular Ca(2+) regulation associated with Pkd2 haploinsufficiency is directly related to the vascular phenotype.

Association of mutation position in polycystic kidney disease 1 (PKD1) gene and development of a vascular phenotype

BACKGROUND

Patients with autosomal dominant polycystic kidney disease (ADPKD) are at risk of developing intracranial aneurysms, and subarachnoid haemorrhage is a major cause of death and disability. Familial clustering of intracranial aneurysms suggests that genetic factors are important in the aetiology. We tested whether the germline mutation predisposes to this vascular phenotype.

METHODS

DNA samples from patients with ADPKD and vascular complications were screened for mutations throughout the PKD1 and PKD2 genes. Comparisons were made between the PKD1 and PKD2 populations and with a control PKD1 cohort (without the vascular phenotype).

FINDINGS

Mutations were characterised in 58 ADPKD families with vascular complications; 51 were PKD1 (88%) and seven PKD2 (12%). The median position of the PKD1 mutation was significantly further 59 in the vascular population than in the 87 control pedigrees (aminoacid position 2163 vs 2773, p=0.0034). Subsets of the vascular population with aneurysmal rupture, early rupture, or families with more than one vascular case had median mutation locations further 59 (aminoacid position 1811, p=0.0018; 1671, p=0.0052; and 1587, p=0.0003).

INTERPRETATION

Patients with PKD2, as well as those with PKD1, are at risk of intracranial aneurysm. The position of the mutation in PKD1 is predictive for development of intracranial aneurysms (59 mutations are more commonly associated with vascular disease) and is therefore of prognostic importance. Since the PKD1 phenotype is associated with mutation position, the disease is not simply due to loss of all disease allele products.

Recurrence of intracranial aneurysms in autosomal-dominant polycystic kidney disease

BACKGROUND

The natural history of intracranial aneurysms (ICAs) in individuals with autosomal-dominant polycystic kidney disease (ADPKD) is poorly defined.

METHODS

We followed twenty ADPKD subjects, eleven with ruptured and nine with intact ICA, for 15.2 +/- 8.1 years (range, 6.0 to 33.2 years). Initial diagnosis was by four-vessel cerebral angiography in eighteen subjects. Follow-up examinations were four-vessel cerebral angiography in fourteen and magnetic resonance angiography (MRA) in six subjects. We examined the occurrence of new ICAs, an increase in size of existing ICAs, recurrent rupture or surgical intervention, and death.

RESULTS

Age at initial diagnosis of ICA was 37.7 +/- 10.4 years (range, 20.2 to 53.1 years). Seventeen subjects (85%) had an anterior and three (15%) had a posterior ICA at initial diagnosis. On restudy, five subjects (25%) had a significant change, consisting of new ICAs in a different location in all five and an increase in size of an existing ICA in two of the five. All subjects with ruptured ICA and one subject with intact ICA had undergone surgery at the time of initial diagnosis. Ten subjects (50%) underwent further surgery 8.1 +/- 6.1 years later (1.3 to 17 years). No subject died during follow-up and one subject experienced a recurrent RICA (RICA). We were unable to identify risk factors associated with development of a new ICA or increase in size of an existing ICA.

CONCLUSION

Individuals with ADPKD and ICA appear to be at moderate risk for new ICAs and increase in size of existing ICAs; mortality and risk of recurrent rupture, however, appear to be low.

Unruptured intracranial aneurysms: a review

OBJECT

In this article, pathological, radiological, and clinical information regarding unruptured intracranial aneurysms is reviewed.

METHODS

Treatment decisions require that surgeons and interventionists take into account information obtained in pathological, radiological, and clinical studies of unruptured aneurysms. The author has performed a detailed review of the literature and has compared, contrasted, and summarized his findings. Unruptured aneurysms may be classified as truly incidental, part of a multiple aneurysm constellation, or symptomatic by virtue of their mass, irritative, or embolic effects. Unruptured aneurysms with clinical pathological profiles resembling those of ruptured lesions should be considered for treatment at a smaller size than unruptured lesions with profiles typical of intact aneurysms, as has been determined at autopsy in patients who have died of other causes. The track record of the surgeon or interventionist and the institution in which treatment is to be performed should be considered while debating treatment options. In cases in which treatment is not performed immediately, ongoing periodic radiological assessment may be wise. Radiological investigations to detect unruptured aneurysms in asymptomatic patients should be restricted to high-prevalence groups such as adults with a strong family history of aneurysms or patients with autosomal dominant polycystic kidney disease. All patients with intact lesions should be strongly advised to discontinue cigarette smoking if they are addicted.

CONCLUSIONS

The current state of knowledge about unruptured aneurysms does not support the use of the largest diameter of the lesion as the sole criterion on which to base treatment decisions, although it is of undoubted importance.

A case of multiple intracranial aneurysms with unruptured associated aneurysms and newly developed ruptured aneurysm

SUMMARY

We report a case of mirror aneurysms at the middle cerebral artery bifurcation with rupture on the left side. After six years, the patient had subarachnoid haemorrhage from a de novo aneurysm which developed separate from but adjacent to the already present aneurysm on the right side. The mechanism of development of multiple aneurysms, especially of the mirror-image type cannot be explained based only on haemodynamic factors and congenital segmental arterial vulnerability which is generalised than focal is highly likely. The sequence of development of aneurysms in this patient along with existing knowledge regarding rupture of aneurysms in conditions like polycystic kidney disease raise questions about the current trend of treating all patients with coincidental, unruptured aneurysms as they may never bleed from such aneurysms but could still be at risk of SAH from newly developing aneurysms.

Familial clustering of ruptured intracranial aneurysms in autosomal dominant polycystic kidney disease

Ruptured intracranial aneurysm (RICA) is a life-threatening complication of autosomal dominant polycystic kidney disease (ADPKD). A family history of RICA may be a risk factor for RICA. Six hundred eight adult members of 199 ADPKD families were interviewed, and family pedigrees were constructed. Individuals were classified as having definite, probable, or possible RICAs from evidence and history obtained in interviews. Central nervous system (CNS) events not consistent with RICA were classified as other CNS events. Seventy-seven CNS events occurred in 906 subjects with ADPKD (8.5%) versus 13 events in 823 subjects without ADPKD (1.6%; P < 0.0001). No event in subjects without ADPKD was consistent with an RICA. Twenty-seven other (non-RICA) CNS events occurred in subjects with ADPKD (3%) versus 13 events in subjects without ADPKD (1.6%; P = 0.05). The frequency of RICA was increased in subjects with ADPKD: 21 definite RICAs in subjects with ADPKD (2%) versus none in subjects without ADPKD (P < 0.001); 28 definite and probable RICAs in subjects with ADPKD (3%) versus none in subjects without ADPKD (P < 0.001); and 50 definite, probable, and possible RICAs in subjects with ADPKD (5.5%) versus none in subjects without ADPKD (P < 0.001). The null hypothesis that RICAs are randomly distributed among subjects with ADPKD was tested for definite RICAs (n = 21), definite and probable RICAs (n = 28), and definite, probable, and possible RICAs (n = 50). In the three categories, the null hypothesis was rejected at P less than 0.05, P less than 0.05, and P less than 0.005, respectively. Vascular CNS events occurred more frequently in ADPKD than non-ADPKD family members, and clustering of RICAs occurred in families with ADPKD.

A giant internal carotid-posterior communicating artery aneurysm presenting with atypical trigeminal neuralgia and facial nerve palsy in a patient with autosomal dominant polycystic kidney disease: a case report

BACKGROUND

In cases of internal carotid-posterior communicating artery (IC-PC) aneurysm, involvement of the trigeminal nerve at its root is rare, and facial nerve palsy is even more unusual.

CASE REPORT

A large, unruptured IC-PC aneurysm was detected in a 56-year-old man with autosomal dominant polycystic kidney disease (ADPKD), but surgery was not performed because of mild renal dysfunction. Two months later, a sudden, severe headache suggested a subarachnoid hemorrhage, which was ruled out by computed tomography and lumbar puncture. Neurological examination revealed complete oculomotor palsy, atypical trigeminal neuralgia, and facial palsy with gustatory disturbance. Magnetic resonance (MR) imaging revealed a partially thrombosed giant aneurysm that directly compressed the trigeminal nerve root, reached the internal auditory canal, and was adjacent to the facial nerve. The neck of the aneurysm was successfully clipped via a subtemporal transtentorial approach. The postoperative course was uneventful, and all neurological symptoms had resolved within 3 months.

CONCLUSIONS

We believe that the prosopalgia in this case was atypical trigeminal neuralgia due to direct compression of the trigeminal nerve root by the aneurysmal sac. A contributory cause was stretching of the oculomotor nerve, which contains sensory afferent inhibitory fibers derived from the ophthalmic branch of the trigeminal nerve. The facial palsy was of peripheral type and was accompanied by gustatory disturbance. This is the first reported case of facial palsy caused by an IC-PC aneurysm and also a very rare case of an IC-PC aneurysm clipped by a subtemporal transtentorial approach.

Aneurysmal disease in children. Review of 20 cases with intracranial arterial localisations

SUMMARY

Twenty children (13 males, 7 females), referred to our group with non traumatic intracranial aneurysms between 1978 and January 1997, were included in this study. Their angiograms were reviewed to assess number, location, type of aneurysms and evolution before and after treatment. Their ages ranged from 1 month to 15 years. Seven patients (35%) presented with subarachnoid haemorrhage (SAH). Eleven patients (55%) presented with focal neurological deficits or seizures: epileptic seizures occurred in five patients, neurologic deficits or focal symptoms due to mass effect occurred in six. Total number of diagnosed intracranial aneurysms was 24. The most common sites involved were internal carotid (37%) and vertebrobasilar (32%) systems. The aetiology of the aneurysms was infective in four patients and unknown in the remaining 16 patients (80%). Endovascular treatment was successful in seven patients (37%). Three patients (15%) were surgically treated. Seven patients (35%) were conservatively treated. Two patients (10%) had spontaneous thrombosis of the aneurysm. SAH was more frequent in males, and never occurred in children under five years old. Frequent presentations such as focal symptoms or mass effect and less prevalence of aneurysm rupture are probably due to the high prevalence of large or giant aneurysms (25%) in our series. In conclusion, radiological findings and the natural history of symptomatic arterial aneurysms in children are clearly different from those in adults. Probably pathogenetic factors and aetiology are also different. Shear stresses, haemodynamic and hormonal factors do not appear to be dominant to reveal such defects, though their correction favours repair. Since repair is frequent, conservative treatment has a major role in their aneurysm management.

Molecular genetics and pathogenesis of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a common and systemic disease characterized by formation of focal cysts. Of the three potential causes of cysts, downstream obstruction, compositional changes in extracellular matrix, and proliferation of partially dedifferentiated cells, evidence strongly supports the latter as the primary abnormality. In the vast majority of cases, the disease is caused by mutations in PKD1 or PKD2, and appears to be recessive at the cellular level. Somatic second hits in the normal allele of cells containing the germ line mutation initiate or accelerate formation of cysts. The intrinsically high frequency of somatic second hits in epithelia appears to be sufficient to explain the frequent occurrence of somatic second hits in the disease-causing genes. PKD1 and PKD2 encode a putative adhesive/ion channel regulatory protein and an ion channel, respectively. The two proteins interact directly in vitro. Their cellular and subcellular localization suggest that they may also function independently in a common signaling pathway that may involve the membrane skeleton and that links cell-cell and cell-matrix adhesion to the development of cell polarity.

Vascular expression of polycystin-2

The expression of polycystin-1 in the vascular smooth muscle cells (VSMC) of elastic and large distributive arteries suggests that some vascular manifestations of autosomal-dominant polycystic kidney disease (ADPKD) result directly from the genetic defect. Intracranial aneurysms have been reported in PKD2, as well as in PKD1 families. To determine whether the vascular expression of polycystin-2 is similar to that of polycystin-1, the expression of PKD2 mRNA and protein in cultured pig aortic VSMC was studied and immunofluorescence and immunohistochemistry were used to study the localization of polycystin-2 in cultured pig aortic VSMC, pig ascending thoracic aorta, and normal elastic and intracranial arteries and intracranial aneurysms obtained at autopsy from patients without or with ADPKD. Tissues derived from Pkd2 wild-type and Pkd2 null mice were used to confirm the specificity of the immunostaining for polycystin-2. Northern blots of VSMC revealed the expected 5.3-kb band. Western blotting detected a 110-kb band in a 100,000 x g fraction of VSMC homogenates. Cultured VSMC as well as VSMC between the elastic lamellae of pig thoracic aorta were positive for polycystin-2 by immunofluorescence. The staining pattern was cytoplasmic. Treatment of the cells before fixation with Taxol, colchicine, or cytochalasin-D altered the pattern of staining in a way suggesting alignment with the cytoskeleton. The immunohistochemical staining for polycystin-2 was abolished by extraction with 0.5% Triton X-100, indicating that polycystin-2 is not associated with the cytoskeleton. Weak immunoreactivity for polycystin-2, which was markedly enhanced by protease digestion, was detected in formaldehyde-fixed normal human elastic and intracranial arteries. Immunostaining of variable intensity for polycystin-2, which was not consistently enhanced by protease digestion, was seen in the spindle-shaped cells of the wall of the intracranial aneurysms. The similar expression of polycystin-1 and polycystin-2 in the vascular smooth muscle is consistent with the proposed interaction of these proteins in a single pathway. These observations suggest a direct pathogenic role for PKD1 and PKD2 mutations in the vascular complications of ADPKD.

Autosomal dominant polycystic kidney disease-type 2. Ultrasound, genetic and clinical correlations

BACKGROUND

Ultrasound, genetic and clinical correlations are available for ADPKD-1, but lacking for ADPKD-2. The present study was carried out to address: (i) the age-related diagnostic usefulness of ultrasound compared with genetic linkage studies; (ii) the age-related incidence and prevalence of relevant symptoms and complications; and (iii) the age and causes of death in patients with ADPKD-2.

METHODS

Two hundred and eleven alive subjects, from three ADPKD-2 families at 50% risk, were evaluated by physical examination, consultation of hospital records, biochemical parameters, ultrasound and with genetic linkage and DNA mutation analyses. Nineteen deceased and affected family members were also included in the study.

RESULTS

Of the 211 alive members, DNA linkage studies and direct mutation analyses showed that 106 were affected and 105 were not. Ultrasound indicated 94 affected, 108 not affected and nine equivocal results in nine children under the age of 15. For all ages, the false-positive diagnostic rate for ultrasound was 7.5% and the false-negative rate was 12.9%. The difference between ultrasound and DNA findings was most evident in children aged 5-14 years where the ultrasound was correct in only 50% and wrong or inconclusive in the remaining 50%. The mean age of the 106 alive, ADPKD-2 genetically affected patients was 37.9 years (range: 6-66 years). Among them, 23.5% had experienced episodes of renal pain, 22.6% were treated for hypertension, 22.6% had experienced at least one urinary tract infection, 19.8% had nephrolithiasis, 11.3% had at least one episode of haematuria, 9.4% had asymptomatic liver cysts, 7.5% had developed chronic renal failure and 0.9% had reached end-stage renal failure. Of the 19 deceased members, nine died before reaching end-stage renal failure at a mean age of 58.7 years (range: 40-68 years), mainly due to vascular complications, while the remaining 10 died on haemodialysis at a mean age of 71.4 years (range: 66-82 years).

CONCLUSIONS

DNA analysis is the gold standard for the diagnosis of ADPKD-2, especially in young people. Ultrasound diagnosis is highly dependent on age. Under the age of 14, ultrasound is not recommended as a routine diagnostic procedure, but ultrasound becomes 100% reliable in excluding ADPKD-2 in family members at 50% risk, over the age of 30. ADPKD-2 represents a mild variant of polycystic kidney disease with a low prevalence of symptoms and a late onset of end-stage renal failure.

Rupture of a previously documented small asymptomatic intracranial aneurysm in a patient with autosomal dominant polycystic kidney disease. Case report

Intracranial aneurysms are common extrarenal manifestations of autosomal dominant polycystic kidney disease (ADPKD). Although their natural history is not completely understood, small asymptomatic intracranial aneurysms in patients with ADPKD often are not treated but are followed with serial magnetic resonance (MR) angiography. The authors report the unique case of a patient with ADPKD who bled from a previously documented asymptomatic 3-mm intracranial aneurysm. This 42-year-old man with ADPKD suffered a subarachnoid hemorrhage (SAH) from a 7-mm left pericallosal artery aneurysm. This aneurysm was clipped and the patient made an excellent recovery. An irregular asymptomatic 3-mm right middle cerebral artery (MCA) aneurysm had also been demonstrated on angiography. While the patient was considering elective surgery for the MCA aneurysm, he suffered a hemorrhage from this lesion 10 weeks after the initial SAH. The aneurysm was clipped and the patient made a satisfactory recovery (he was moderately disabled). In this report the authors indicate that small asymptomatic intracranial aneurysms are not always innocuous in patients with ADPKD, and they suggest that treatment should be strongly considered for these lesions in this group of patients when there is a history of SAH or the aneurysm is irregular in appearance. Because MR angiography studies may not adequately define the configuration of small aneurysms and irregularity may easily be missed, conventional angiography is recommended for patients with ADPKD who are found to have an intracranial aneurysm on screening with MR angiography.

Genetics of intracranial aneurysms

The etiology and pathogenesis of intracranial aneurysms are clearly multifactorial, with genetic factors playing an increasingly recognized role. Intracranial aneurysms have been associated with numerous heritable connective tissue disorders, which account for at least 5% of cases. Of these disorders, the most important are Ehlers-Danlos syndrome Type IV, Marfan's syndrome, neurofibromatosis Type 1, and autosomal dominant polycystic kidney disease; the association with intracranial aneurysms, however, has been firmly established only for polycystic kidney disease. Familial intracranial aneurysms are not rare but account for 7 to 20% of patients with aneurysmal subarachnoid hemorrhage and are generally not associated with any of the known heritable connective tissue disorders. First-degree relatives of patients with aneurysmal subarachnoid hemorrhage are at an approximately fourfold increased risk of suffering ruptured intracranial aneurysms, compared to the general population. Various possible modes of inheritance have been identified in families with intracranial aneurysms, suggesting genetic heterogeneity. Although the benefits have never been quantified, screening for asymptomatic intracranial aneurysms should be considered in families with two or more affected members. The yield of such a screening program may approximate 10%. Although it is unlikely that there is a single gene with major effect, much effort is currently being directed at locating intracranial aneurysm genes.

Is family history an independent risk factor for stroke?

OBJECTIVE

To estimate the influence of family history on the occurrence of stroke.

METHODS

A case-control study was carried out from August 1992 to January 1994. The study population comprised 502 patients with a first stroke, aged between 20 and 70 years, who were treated at 48 affiliated hospitals. The same number of age and sex matched controls were selected from outpatients. Diagnoses were based on CT findings and clinical signs. There were 155 case-control pairs for subarachnoid haemorrhage, 158 for intracerebral haematoma, and 159 for cerebral infarction. Information about the patients and their families was obtained from a questionnaire which included the family histories of each subtype of stroke and other potential risk factors for stroke. The data were analysed focusing on the role of the family histories in the occurrence of stroke.

RESULTS

In univariate analysis, the family histories of subarachnoid haemorrhage and intracerebral haematoma were positively associated with each of the subtypes of stroke (odds ratios 11.24 for subarachnoid haemorrhage, 2.39 for intracerebral haematoma), whereas family history of cerebral infarction was not a significant risk factor for its occurrence (odds ratio 1.41). Family history of intracerebral haematoma was correlated with a personal history of hypertension and habitual alcohol consumption. After adjustment for potential risk factors (hypertension, diabetes, hyperlipidaemia, obesity, alcohol consumption, and regular smoking), family history of subarachnoid haemorrhage still remained the most powerful risk factor for subarachnoid haemorrhage, whereas family history of intracerebral haematoma no longer showed a significant association with haematoma.

CONCLUSION

Genetic factors play a major part in the pathogenesis of subarachnoid haemorrhage, and family history of subarachnoid haemorrhage is the strongest independent risk factor for the disease. On the other hand, family history of intracerebral haematoma was not an independent risk factor for haematoma, but it might be a good predictor, which indirectly influences the pathogenesis of intracerebral haematoma via certain hereditary components such as hypertension, and even lifestyle factors such as alcohol consumption. In cerebral infarction, genetic factors play a minor part in its pathogenesis.

Patients with polycystic kidney disease would benefit from routine magnetic resonance angiographic screening for intracerebral aneurysms: a decision analysis

Autosomal dominant polycystic kidney disease (ADPKD) is associated with increased prevalence of cerebral aneurysms and increased risk of subarachnoid hemorrhage. A decision analysis by Levey et al. in 1983 demonstrated that patients with ADPKD would not significantly benefit from routine arteriographic screening for cerebral aneurysms. We reexamined this conclusion in light of new clinical data and the introduction of magnetic resonance imaging (MRI) as a screening method. We compared an MRI screening strategy with a nonscreening strategy. The screening strategy specified MRI screening and then neurosurgical management of detected aneurysms. The nonscreening strategy specified cerebrovascular care only in the event of subarachnoid hemorrhage. The decision tree incorporated estimates derived from the clinical literature for the prevalence of asymptomatic aneurysms in patients with ADPKD (15%), the annual incidence of aneurysmal rupture (1.6%), the morbidity and mortality rates associated with subarachnoid hemorrhage (70 and 56%, respectively), the risk of transfemoral arteriography (0.2%), the sensitivity and specificity of MRI, the morbidity and mortality rates associated with surgical treatment of an unruptured aneurysm (4.1 and 1.0%, respectively), and the life expectancy of patients with ADPKD. The model predicted that the screening strategy would provide 1.0 additional year of life without neurological disability to a 20-year-old patient with ADPKD. A sensitivity analysis showed that the model was most sensitive to estimates of the prevalence of aneurysms in ADPKD, the annual incidence of rupture, and the morbidity and mortality rates associated with rupture. A financial analysis showed that a screening strategy is likely to cost less than a nonscreening strategy. The model predicts that an MRI screening strategy would increase the life expectancy of young patients with ADPKD and reduce the financial impact on society of ADPKD.