The term “ICSOL” includes lesions which expand in volume to displace normal neural structures and lead to increased intracranial tension. These lesions give rise to the following three groups of symptoms in general.
1. Neurological phenomena caused by irritation or destruction of brain tissue, eg focal seizures (Jacksonian epilepsy) and paralysis.
2. Characteristics of elevated intracranial tension (TIC): The rate of increase in blood pressure and its level depend on the nature of the lesion and its location. For example, rapidly growing tumors and secondary multiples give rise to a rapid increase in TICs while slow growing tumors and cysts can be lodged in the skull for considerable periods without symptoms. Moreover, in general, lesions of the posterior fossa lead to a rise in blood pressure more rapidly than supratentorial lesions.
3. False signs of localization:
(a) These are neurological phenomena resulting from the side effects of lesions. As a result of a herniation of neural tissue under the cerebral falx or a descending hernia through the tentorium cerebrlli and foramen magnum, pressure effects on other parts of the brain develop.
(b) Counter-Cup Effect: This is a pressure effect caused on the side opposite to the lesion side when a lesion occupying a space expands. Midline structures such as the brainstem can be pushed to the opposite free margin of tentorum cerebelli to give rise to compression on the normal side as well. In addition to these characteristic genera, different lesions can produce symptoms specific to their nature. For example, a brain abscess can be associated with fever and other signs of infection. Subarachnoid hemorrhage may be associated with meningeal signs or irritation.
Clinical features: About 50-60% of neurological disorders in India are lesions occupying space. Persistent headaches that are not due to any other detectable cause and that do not respond to a single medication should suggest a possibility of ICSOL. The headache can be felt in the midline above the head or sometimes it can be referred to the site of the injury, for example the meningioma. It can be continuous and gradual, paroxysmal (as in migraine) or worsened by coughing, bending forward or changing postures.
Vomiting and visual loss: In many cases, prolonged vomiting is a common symptom. Projectile vomit can be moistened in gastrointestinal or psychiatric disorders. Vision failure due to papilliedema is a late occurrence in most cases. The recent onset of behavioral changes and the sudden onset of neurological deficits are also clinical features.
Late onset of seizures: Any type of seizure occurring for the first time after the age of 15 should suggest the possibility of ICSOL.