Serious complications (catastrophes) resulting from diverse neurological 
diagnostic procedures can be caused by erroneous indication and omission, as 
well as by delay and erroneous execution or interpretation. Headache, caused by 
cerebrospinal fluid (CSF) hypotension, is a frequent complication of lumbar 
puncture; hematic patch is a therapeutic option for severe cases. The most 
serious complication is cerebral herniation and, for its prevention, computed 
tomography (CT) or cerebral magnetic resonance imaging (MRI) must always be 
performed before lumbar puncture: a lesion with evident mass effect is a 
contraindication. Some cases of minor subarachnoid hemorrhages can produce 
sentinel headache: when the findings of CT scans are normal, lumbar puncture 
must be performed for diagnosis and prevention of a catastrophic recurrence. 
Edrophonium testing can be complicated with bradycardia and/or asystole. The 
lack of indication of this procedure is a cause of under-diagnosis of myasthenia 
gravis, especially in older people. Electromyography produces few complications 
(rare cases of paraspinal hematomas and pneumothorax). Ultrasound, CT 
angiography and MR angiography examinations have decreased the indications for 
cerebral angiography, whose main complications -in addition to contrast 
reactions, hemorrhage and infection at the injection site- are neurological 
deficits caused by vascular dissection or atheromatous embolus. 
Video-electroencephalogram (EEG) recording with medication suppression can be 
used in the presurgical evaluation of epilepsy, which can precipitate repeated 
seizures with the risk of injuries and status epilepticus. The possible 
complications of studies performed with invasive electrodes are infections and 
intracranial hemorrhages. Cerebral biopsy is indicated when treatable disease is 
suspected but the therapeutic options (radiotherapy, chemotherapy) have 
potential serious adverse effects. Furthermore, cerebral biopsy can aggravate 
previous neurological deficits or produce new deficits. Genetic testing is not 
indicated in healthy children when an untreatable disease is suspected. In 
adults, genetic testing is appropriate in selected cases, but detailed previous 
information should be gathered and the possibility of triggering serious 
emotional reactions should always be considered.