D = drug-induced
E = emotions (depression especially)
M = metabolic and endocrine issues
E = eyes and ears (sensory problems)
N = nutritional issues (B12 and Vit. D)
T = tumors
I = infections
A = alcohol
S = sleep disorders and rarely seizures
Degenerative
Alzheimer's disease
Huntington's disease
Parkinson's disease
Vascular
Multiple infarcts
Hypoperfusion (MI, profound hypotension)
Subdural hematoma
SAH
Infectious
Meningitis (sequelae of bacterial, fungal, or tubercular)
Neurosyphilis
Viral encephalitis (HSV, HIV), Creutzfeldt-Jakob disease
Inflammatory
SLE
Demyelinating disease (e.g. multiple sclerosis)
Neoplastic
Primary brain tumor / metastatic disease
Carcinomatous meningitis
Paraneoplastic syndromes
Traumatic
Traumatic brain injury
Subdural hematoma
Toxic
ETOH 
Meds (anticholinergics, polypharmacy)
Metabolic
B12 deficiency or folate deficiency
Thyroid Disease
Uremia
Psychiatric
Depression (pseudodementia)
Hydrocephalic
Normal pressure hydrocephalus (communicating hydrocephalus)
Noncommunicating hydrocephalus
Alzheimer's disease
Huntington's disease
Parkinson's disease
Multiple infarcts
Hypoperfusion (MI, profound hypotension)
Subdural hematoma
SAH
Meningitis (sequelae of bacterial, fungal, or tubercular)
Neurosyphilis
Viral encephalitis (HSV, HIV), Creutzfeldt-Jakob disease
SLE
Demyelinating disease (e.g. multiple sclerosis)
Primary brain tumor / metastatic disease
Carcinomatous meningitis
Paraneoplastic syndromes
Traumatic brain injury
Subdural hematoma
ETOH 
Meds (anticholinergics, polypharmacy)
B12 deficiency or folate deficiency
Thyroid Disease
Uremia
Depression (pseudodementia)
Normal pressure hydrocephalus (communicating hydrocephalus)
Noncommunicating hydrocephalus
Dementia with Lewy bodies
D = drug-induced
Normal pressure hydrocephalus
E = emotions 
Prion disease
M = metabolic and endocrine issues
Parkinson's disease
E = eyes and ears 