Recreational drugs and their neurological consequences

his article deals with neurological problems following the use of recreational drugs and substances as they present to neurologists.The effects of alcohol and the details of neuropsychiatric and neuropharmacological effects of recreational drugs are not considered. CLINICAL FEATURES cIt is sometimes difficult to attribute a particular clinical syndrome to a particular drug type.Certain common features emerge which may be related directly and specifically to the drug (as outlined later) but other clinical features may arise in a non-specific way from complications of injection and/or coma.Furthermore addicts may use more than one drug (wittingly or unwittingly), each of which they may describe by a variety of ''street'' names which are far from standard (table 1).Moreover, the dose and the constituents of what they actually take (in terms of contaminants and other substitutes) may vary according to the source, batch, etc. Lastly the effects of the drug may vary considerably according to the method of intake (orally, nasally, inhalation/smoking or by intravenous, intramuscular, or subcutaneous injection), and they may be intensified by coincidental alcohol use.All these factors may produce a variable clinical picture which cannot be relied upon to indicate that drug abuse is the cause.Conversely and on a more practical note, the recognition of drug addiction should raise suspicion that the presenting neurological syndrome may have an unusual aetiology and pathogenesis, and be a warning for the neurologist that there is the potential for more than one pathology, and that future management may have predictable difficulties.Certain common clinical themes are useful (table 2), partly because their recognition may act as a ''red flag'' for drug abuse (marked with an asterisk in table 2). WHY THINGS GO WRONGObviously in almost all instances of drug misuse, the effects of the drug wear off without mishap.However, problems may arise directly due to the drug, under the influence of a number of interacting factors, or indirectly by other mechanisms (table 3).Identifying these in individual cases is very difficult. ''WHERE IS THE LESION AND THEN WHAT IS THE LESION?''Any level of the nervous system may be affected, from the cortex to the neuromuscular junction, and this old adage is even more pertinent than usual.There is a tendency to take the initial clue of drug misuse and to jump to conclusions about pathologies, and thence location.It is essential that the location(s) of the lesion(s) is worked out first in the normal way, with the history of drug addiction then being introduced to bring in any ''extra'' pathologies which might explain this lesion, over and above those in non-users. PARTICULAR NEUROLOGICAL SYNDROMESSome of the more common neurological syndromes in drug addicts are outlined in table 4.However, it should always be remembered that drug addicts are at much greater risk of having alcohol abuse problems and/or HIV infection, both of which are associated with their own blend of neurological syndromes and which may co-exist or subsequently develop (for example, alcohol withdrawal fits).Once their drug addiction is recognised, addicts often deny alcohol abuse, just as they often claim that they have never injected, or no longer do so.I always regard such assertions with great scepticism, and allow for these possibilities. CLINICAL EFFECTS OF RECREATIONAL DRUG GROUPSThere are five broad groups of recreational drugs: c The stimulants c The sedatives c The hallucinogens c The organic solvents c Drugs used to enhance athletic performance iii9