Probable Vascular Dementia in the Tropics: A Study of Twenty-Six (26) Observations at Conakry University Hospital

Introduction: In tropical environments, the diagnostic certainty of vascular dementia is difficult to establish due to under-medicalization, delays in consultation and above all the inadequacy of exploration methods. Material and methods: We analyzed the records of 153 patients hospitalized for dementia syndrome over a period from January 1, 2016 to December 21

Most of these works reveal the theoretical and practical difficulties raised by the nosology of this vascular pathology entity and its boundaries with other conditions in which vascular lesions may be involved in their outbreak: Alzheimer's disease, mixed dementias [8].
In sub-Saharan Africa, due to delays in consultation and management of vascular pathologies, dementia sets in gradually, and its etiological dismemberment is not easy [9].
We report a series of 26 patients in whom vascular disease led to the emergence of dementia certified by psychometric and imaging tests.We studied the clinical, biological and neuroradiological profiles of these patients in order to better define their characteristics in tropical environments.Thus, we report 26 cases of presumed vascular dementia occurring in Conakry between 2016 and 2021 with the aim of re-evaluating this pathology from a clinical and etiological point of view.The interest of this work lies in the fact that these observations illustrate vascular dementias and the diagnostic difficulty they entail in tropical environments within the vast group of subcortical dementias.

Material and methods
This is a prospective descriptive and analytical study lasting 5 years, from January 1, 2016 to December 31, 2021, and involving all patients hospitalized in the neurology department of Conakry University Hospital for dementia.Inclusion criteria were as follows: -Patients presenting a dementia syndrome according to the DSM-IV criteria [10] published by the National Institute of Neurological Disorder and Stroke and those of ICD-10 [11].
-These criteria are underpinned by the association of dementia and cerebrovascular disease, certified by a Hachinski score [1]: 0 and 4 signs of degenerative dementia, and 7 and 8 points of multiple infarct dementia.
With a view to detecting the vascular cause, the following investigations were also carried out: -All subjects underwent a series of complementary examinations: CBC, VS, fasting blood glucose, 24   All patients underwent a neurological and psychiatric examination and, depending on their clinical orientation, an otolaryngological examination using the FNL-10KP3 laryngoscope (Pentax, France), an ophthalmological examination using the IEC LR6,300 HEINE MINI ophthalmoscope (Germany) and a fundus examination.All these investigations enabled us to identify the conditions responsible for cerebral vasculitis: Sussac syndrome, Cogan's disease.
All patients underwent two electroencephalographic examinations using a Nippon neurofax Japan head box EEG at the start and end of their stay.

Results
Analysis of the results of this study focused on clinical, neuroradiological and electroencephalographic data.All 26 patients met the DSM-IV and ICD-10 criteria ¬labelled by the WHO in 1993, and these criteria were underpinned by the existence of a dementia syndrome, cerebrovascular involvement and the existence of a link between the two elements.Table I summarizes the main relationships between sociodemographic characteristics and potential risk factors for the onset or existence of vascular dementia.

CLINICAL SIGNS IN THE EARLY PHASE PROPORTION
Slow progressive onset      In Binswanger disease, MRI reveals diffuse but heterogeneous white matter involvement in the periventricular regions, and discrete images of cortical atrophy.
Diagnostic certainty is neuropathological.

Electroencephalographic Data
A non-specific alteration of the EEG tracings (type II) was detected in 24 patients (85.7%) with no specific abnormalities, in contrast to 4 patients (14.2%) with epileptic seizures (type III) in our classification.(Fig 9).

Discussion
This study reports 26 probable cases of vascular dementia diagnosed at the University Hospital of Conakry according to DSM-IV [15] and NINDS-AIREN [16] criteria.These are all presumed cases, some of which were diagnosed in the neurology department.Classically, the clinical diagnosis of vascular dementia is based on three elements [10,11,12], including the existence of a certified dementia syndrome [13], cerebrovascular involvement and the presence of a link between the two [14].
In 1974, Hachinski et al [1] proposed a score in favour of a vascular origin for these dementias, in contrast to degenerative dementias.The certainty of this link remains debatable, and has given rise to a number of controversies, some of which cast doubt on the existence of vascular dementia [17], with several different designations: multiple infarcts [18] arteriopathic dementia [19], non-dementia cognitive disorders of vascular origin [20], highlighting the lack of consensus on definition, pathophysiology and diagnosis [21].Underlying these various controversies is the lack of reliable pathological criteria for differentiating vascular dementia from mixed vascular and degenerative dementia [22,15].
On the other hand, the certainty of differentiating vascular dementia from Alzheimer's disease, a clinico-biological entity characterized by neuropathological lesions biologically characterized by biomarkers of beta amyloid pathology (low AB42 levels in cerebrospinal fluid or increased AB40-AB42 ratio in CSF : increased retention of the amyloid PET tracer) and biomarkers of tau pathology (increased phosphorylated TAU in CSF: increased retention of the tau PET tracer) remains complicated in tropical environments, in the absence of systematized biological explorations.These difficulties are further compounded by the association of vascular lesions in Alzheimer's disease and Lewis bodies.In a documented series on CSF protein biomarkers in dementia, Gabelle et al have drawn up a comparative table of expected variations according to dementia type [32].
Despite the high frequency of studies on vascular accidents in sub-Saharan Africa [9][10][11][12][13][14][15] and the diagnostic difficulties of vascular dementia, epidemiological data are non-existent in tropical environments and variable in international data depending on the criteria used.Nevertheless [16,17] estimate that vascular dementia is the leading cause of dementia in developing countries in Africa and Asia, essentially due to inadequate prevention and management of cardiovascular disease [18,19] note that the prevalence of vascular dementia is in the order of 8 to 13%, in contrast to mixed dementias at 12 to 25% [20], with an estimated incidence of 2.52 per 1000 inhabitants.
In sub-Saharan Africa, data are patchy and poorly documented [27], and this study is the first to our knowledge to describe probable cases of vascular dementia.
Generally speaking, the clinical pictures of vascular dementia observed in this study do not differ fundamentally from those described in the literature [21,22], with two entities dominated by multiple infarcts and Binswanger's disease.
The vascular dementias observed in this study correspond to the known clinical and neuroradiological characteristics of this condition: presence of lesions of vascular origin on cerebral imaging, reported existence of vascular accidents with focal signs more or less associated with a supra bulbar syndrome, and a temporal relationship between the stroke and cognitive dementia [29].In addition, we noted frequent and recurrent auditory hallucinations and illusions, likely expressions of epileptic discharge in the T1 and T2 convolutions and Amon's horn, and in a second patient, repetitive complex visual hallucinations associated with language disorganization due to epileptic discharge in the dominant hemisphere following lacunae in the temporal convexity and involving the anterior part of the temporal lobe.These epileptiform syndromes have been observed in patients with multiple lacunae, and are thus consistent with the semiology of vascular epilepsy.
In Africa, under-medication is a further explanation for the severity of the cognitive disorders observed, which are more often than not diagnosed late.In tropical environments, dementia is also mostly multifactorial, hence the importance of an extensive work-up: coronal cross-sectional brain imaging of the hippocampi, CBC, CRP, liver function tests, ionograms, vitamin B12, plasma folate, TSH-US, VDRL-TPHA, HIV serology, PCR for Tropheryma Whippeli, etc.
Our study also shows the importance of MRI in vascular dementia, despite the fact that Pierre Marie lacunar state, Binswanger's disease and leukoaraiosis are associated anatomoradiological entities.In axial flair and sagittal sections, it shows intense hypersignals, sometimes very marked, in the supratentorial white matter at the level of the oval and supratentorial cortical centers and in the periventricular area, as demonstrated by our study and many others [30].Some authors note the existence of hyperintense signals in insular regions and in the gray nuclei [31].

Conclusion
This study shows the presence and persistence of vascular dementia in Africa, and the diagnostic difficulty it entails in tropical environments due to the high frequency of strokes caused by inadequate prevention and management of notified risk factors.

Apical 4 -
cavity section showing a voluminous apical intra-VG thrombus Two-dimensional long-axis section with TM showing LV dilatation ECG: recording a complete arrhythmia due to AF

Figure 3 . 4 .
Figure 3. Multiple infarction with bi-carotid stenosis Figure 4. Diffuse but heterogeneous white matter in periventricular regions, images of cortical atrophy.

Table 2 .
Clinical signs at onset and advanced stage disease