It is very important to make a correct diagnosis of stroke syndromes as the management of the first four to five days determines the outcome of the patient. The proper and correct diagnosis requires the following steps to be established in the sequential order :
- Is it a stroke ?
- If it is a stroke then what type is it ?
- What is the site and extent of the lesion ?
- What is the vascular territory of the lesion ?
- What is the extent of functional impairment of the patient ?
- Are there associated diseases ?
A good working knowledge of the brain and vascular supply is important. The family member and the patient will then be better placed to understand day-to-day-day event in stroke management.
The diagnosis of a stroke at the beside is rarely difficult because the mode of presentation is so distinctive. This is called clinical temporal profile. The symptoms develop abruptly or very rapidly, progress in the next few hours or days to a maximum, and then the clinical condition stabilises. If the patient survives then there is fair degree of improvement. Stroke syndromes may be very mild and may consist of trivial neurological signs and may not draw the patient attention to seek medical advice as happens in transient ischaemic attacks. But it may also manifest with such abruptness that the patient may slip into coma in a few minutes and die as may happen in massive intracerebral haemorrhage or sub-araachnoid haemorrhage. There are all grades of severity between these two extremes.
Once the diagnosis of a stroke syndrome is suspected, the neurologist would like to know and establish the type of stroke at the bedside. This seldom presents much difficulty. Some of the important and frequent conditions have been discussed earlier. These have characteristic evolution and temporal profile and pose no great problem. Transient ischaemic attacks, ischaemic thromoboembolic strokes, intracerebral haemorrhage, and venous infarcts can be diagnosed. It is the clinical setting in which these stroke syndromes develop that is important for their identification. A stroke following an uncontrolled hypertension is more likely to be caused by intracerebral haemorrhage.
Neurologists would also like to establish the site and extent of the lesion in every stroke syndrome. All functions are located somewhere in the brain at different sites. Anatomical location of these functions is an important prerequisite for establishing the site of lesion. Examination of the cranial nerves is an important exercise as these are distinctly located in the brain. We also know that motor and sensory functions are located on the opposite sides of the brain. Complications of pathological lesions like cerebral oedema, herniation of brain, displacement of brain, compression of vascular channels, etc. may produce their effect and exhibit new signs and symptoms. These would complicate the original symptoms and signs and make diagnosis difficult. Therefore, proper investigation and awareness and knowledge of the events that are taking place are essential for the diagnosis and management of neurovascular syndromes.
Motor weakness, that is, inability to move limbs in one half of the body, may result from several sites within the brain. At one site a tiny lesion may produce a dense motor weakness while at another site the lesion has to be of large size to produce a similarly dense motor weakness. This has got great bearing on the recovery after a stroke. Therefore, the treating doctor should try to establish the functional disturbance at a given time in every case.
It is usually important to know and establish the alterations on other organs like heart,lung, stomach or metabolic functions from the brain lesions or stroke syndromes. Some ECG charge are common in stroke syndromes and can be interpreted as ischaemic heart disease. There may be stress ulcers in stomach and can lead to bleeding. A rise in sugar levels in blood and urine is quite frequent in stroke patients and at times may be quite marked in latent diabetic patients and accordingly would require necessary medical management. Electrolyte disturbances, poor intake of fluids may have effect on other systems as well as on the brain. Therefore, laboratory investigations and other diagnostic methods for assessing the systemic diseases or their involvement are important in the total management of the stroke syndromes.
The role of correct diagnosis in clinical medicine is indisputable. The correct diagnosis not only saves life or reduces morbidity but greatly influences the health economics. Sequential diagnostic goals have been identified in the management of stroke syndromes in the previous pages. Correct diagnosis requires proper investigations at the right time. There are several investigations available : some are cheap and others are relatively expensive. It is understandable that all investigations can not be ordered in every case. Choice of investigation and sequence of investigation should best be left to the treating doctor. There are, however, limitations on the choice of investigations in a particular hospital, city or country. Financial constrains also limit the choice of investigations. Therefore, it is very essential for the treating doctor to take all factors into consideration and order the available investigation which can provide the maximum and best information in the management of the patient. It is a good policy to discuss with the family members or the patient the possible investigations and their role in the management of the case.
There are a number of diagnostic tests. These can be divided broadly into two groups : general and special, i.e. specifically related to stroke syndromes. These investigatory tests can also be divided into non-invasive and invasive Computerised tomography has completely revolutionised the diagnostic technologies. Many traditional tests done in the pre-CT era have now been abandoned. General tests may include haematological and biochemical investigations, X-rays, EEG, radioisotope brain scan and cerebro-spinal fluid examination.
CRANIAL COMPUTERISED TOMOGRAPHY
The different parts of the body like the thorax, abdomen now can be examined by the whole body CT scanner. In stroke syndromes we are interested in cranial computerised tomography. Different brain tissue slices are examined in sequential order by X-ray beam and with the help of a computer complete skull pictures are developed. These pictures are taken in different directions for better visualisation of different brain regions and structures. CCT can be done with or without contrast media. In stroke syndromes non-enhanced CT is preferred and should always be first done. Blood vessels can be made visible by infusion of contrast media. CT is very good to differentiate between ischaemia or haemorrhage or to eliminate tumours or subdural haematoma simulating acute vascular episode.
MAGNETIC RESONANCE IMAGING
MRI is based on the application of magnetic field where protons absorb and then re-emit radiowaves. It is possible to change the direction of the magnetic movement of protons by applying to the sample short bursts of radiowaves of a specific frequency. The radiowaves are analysed by computer and pictures are developed for interpretations.
Advantages of MRI include the absence of X-ray exposure, improved contrast between structures and absence of bone artefacts. In many situations MRI is better than CT, particularly in evaluation of brain-stem lesions. MRI gives better anatomical correlation but it is much more expensive. CT and MRI are complementary tests in the evaluation of stroke syndromes. Both are non-invasive and can easily be repeated during the course of illness.
Recently MRI technology has further advanced. Magnetic resonance angiography can partly replace angiography. Without the use of contrast media, radio-frequency signals from flowing blood are used to visualise the cerebro-vascular system. Another advance in MR technology is the development of magnetic resonance spectroscopy. Brain metabolism can be studied by MRS.
The role of arteriography in cerebrovascular diseases has been well established since 1948. It can be used to image the extracranial vasculature in the neck in stroke syndrome, aneurysms, and arteriovenous malformations in the brain and has played a vital role in the surgical management of strokes. It is equally good to demonstrate subdural haematoma. Major advances have taken place in the development of contrast materials and new imaging techniques, such as four-vessels angiography by femoral route which has provided lots of advantages. The technique has been further developed in order to reduce the complications and take better pictures with the help of the computer. This technique is called digital subtraction angiography. This can be done by either injecting contrast material into the vein or into the artery. Venous DSA is an almost non-invassive procedure.
Improvements in electronics and computer technology have greatly helpedin the utilisation of diagnostic ultrasound for the evaluation of stroke syndromes. This technology is non-invasive,relatively inexpensive and safe. It is of two : real time imaging and Doppler imaging. B-mode scanning images the arterial wall, not the moving red blood cells. Doppler scanning image the blood flow velocity through vessels. Duplex scan is the combination of high resolution B-mode imaging with Doppler flow detection. It provides the physiologic information of blood flow with 2-dimensional imaging of the walls of the artery or vein. Transcranial Doppler is a new non-invasive technique to measure the flow velocities through the large intracranial arteries.
Any bedside discussion on stroke syndromes gets confined to the arterial system. Venous pathology as a cause of stroke is either not entertained or overlooked, though these have been known to neurologists for centuries. It is true that venous strokes are very rare. But obstruction in venous outflow can cause stagnation of blood and accumulation of injurious metabolic end products, which in turn can cause tissue damage, leading to a venous stroke.
Blockage by thrombus is the most common cause. The thrombosis may be primary or non-infective, or secondary or infective. Dehydration, blood disorders, hormone effect, tumour growth, etc., all can lead to blockage of a vein. Infection of the veins called phlebitis, commonly leads to formation of thrombus and blockage of the vein lumen. Despite the many potential causes, however, disease of the veins is rather unusual. One reason may be that because of valveless flow the blood flows in either direction and allows instantaneous shunting of blood. In clinical practice, infection of paranasal sinuses or middle ear is knows to result in intracranial spread of infection.
Clinical features of a venous stroke are very variable and include seizures, weakness, paralysis, raised intracranial pressure, sub-arachnoid haemorrhage, or coma. The clinical manifestations depend upon the sinus involved, or superficial or cortical veins. Severe headache, vomiting, or seizures in a patient with infection of paranasal sinuses or middle ear should alert the patient and the doctor and should be investigated. The evidence of infection should be established. CT and MRI are the investigations of choice. Digital subtraction angiography or MRI angiography may show whether the blockage is complete or partial. The use of antibiotics can save many patients. The recovery is rapid and without much residual disability in many patients. Steroids are required at time to reduce the brain oedema. Role of blood anticoagulants and fibronolytic agents in the management of venous stroke is very controversial. Surgical treatment is required if the infection is localised, like brain abscess. Surgical attention will also be required for conditions like severe sinusitis or otitis media, once the brain condition is taken care of. Otherwise, there is the risk of recurrence.
STROKE IN THE YOUNG CAN BE QUITE TRAUMATIC
Stroke as a disease entity is better appreciated in the community by its occurrence in elderly people. Stroke in the young is described as stroke syndromes in persons below the age of 45 years. If one takes all stroke cases in all age groups in the community then it is believed that 15 to 20 per cent cases fall in this group. Stroke in the young cause much more social, economic, and psychological problems. Persons in this age group are mostly bread-winners for the family and the stroke may cripple the family. There are some specific disease conditions leading to strokes which are more common in this age group. For all these reasons stroke in the young is considered separately. One should not forget that primary brain haemorrhage due to hypertension or atherosclerotic ischaemic infarction can also occur within the younger age group.